diff --git a/modules/openapi-generator-cli/src/main/java/org/openapitools/codegen/cmd/GenerateBatch.java b/modules/openapi-generator-cli/src/main/java/org/openapitools/codegen/cmd/GenerateBatch.java
index f2823ce366d8..284022d16e3e 100644
--- a/modules/openapi-generator-cli/src/main/java/org/openapitools/codegen/cmd/GenerateBatch.java
+++ b/modules/openapi-generator-cli/src/main/java/org/openapitools/codegen/cmd/GenerateBatch.java
@@ -148,6 +148,8 @@ public void execute() {
 
         ExecutorService executor = Executors.newFixedThreadPool(numThreads);
 
+        long startTime = System.currentTimeMillis();
+
         // Execute each configurator on a separate pooled thread.
         configurators.forEach(configurator -> {
             GenerationRunner runner = new GenerationRunner(configurator, rootDir, Boolean.TRUE.equals(failFast), Boolean.TRUE.equals(clean));
@@ -163,12 +165,18 @@ public void execute() {
 
             executor.awaitTermination(awaitFor, TimeUnit.MINUTES);
 
+            long elapsedMs = System.currentTimeMillis() - startTime;
+            long minutes = TimeUnit.MILLISECONDS.toMinutes(elapsedMs);
+            long seconds = TimeUnit.MILLISECONDS.toSeconds(elapsedMs) % 60;
+            long millis = elapsedMs % 1000;
+            String elapsed = String.format(Locale.ROOT, "%dm %ds %dms", minutes, seconds, millis);
+
             int failCount = failures.intValue();
             if (failCount > 0) {
-                System.err.println(String.format(Locale.ROOT, "[FAIL] Completed with %d failures, %d successes", failCount, successes.intValue()));
+                System.err.println(String.format(Locale.ROOT, "[FAIL] Completed with %d failures, %d successes in %s", failCount, successes.intValue(), elapsed));
                 System.exit(1);
             } else {
-                System.out.println(String.format(Locale.ROOT, "[SUCCESS] Batch generation finished %d generators successfully.", successes.intValue()));
+                System.out.println(String.format(Locale.ROOT, "[SUCCESS] Batch generation finished %d generators successfully in %s.", successes.intValue(), elapsed));
             }
         } catch (InterruptedException e) {
             e.printStackTrace();
diff --git a/modules/openapi-generator/src/main/java/org/openapitools/codegen/DefaultCodegen.java b/modules/openapi-generator/src/main/java/org/openapitools/codegen/DefaultCodegen.java
index 1ff331cbe6dd..8af0ae7022c7 100644
--- a/modules/openapi-generator/src/main/java/org/openapitools/codegen/DefaultCodegen.java
+++ b/modules/openapi-generator/src/main/java/org/openapitools/codegen/DefaultCodegen.java
@@ -69,6 +69,7 @@
 import org.openapitools.codegen.utils.ExamplesUtils;
 import org.openapitools.codegen.utils.ModelUtils;
 import org.openapitools.codegen.utils.OneOfImplementorAdditionalData;
+import org.openapitools.codegen.utils.PatternCache;
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
 
@@ -79,7 +80,6 @@
 import java.nio.charset.StandardCharsets;
 import java.util.*;
 import java.util.Map.Entry;
-import java.util.concurrent.ConcurrentHashMap;
 import java.util.concurrent.ConcurrentSkipListSet;
 import java.util.concurrent.TimeUnit;
 import java.util.function.Consumer;
@@ -98,8 +98,6 @@ public class DefaultCodegen implements CodegenConfig {
 
     private final Logger LOGGER = LoggerFactory.getLogger(DefaultCodegen.class);
 
-    public static final Pattern SPLIT_ON_SEMICOLON_OR_NEWLINE_REGEX = Pattern.compile("\\s*(;|\\r?\\n)\\s*"); // Splits on semicolon or new line, ignoring surrounding whitespace
-
     public static FeatureSet DefaultFeatureSet;
 
     // A cache of sanitized words. The sanitizeName() method is invoked many times with the same
@@ -245,18 +243,107 @@ apiTemplateFiles are for API outputs only (controllers/handlers).
     // sort operations by default
     protected boolean skipSortingOperations = false;
 
+    // --- MIME type patterns ---
     protected final static Pattern XML_MIME_PATTERN = Pattern.compile("(?i)application/(.*)[+]?xml(;.*)?");
     protected final static Pattern JSON_MIME_PATTERN = Pattern.compile("(?i)application/json(;.*)?");
     protected final static Pattern JSON_VENDOR_MIME_PATTERN = Pattern.compile("(?i)application/vnd.(.*)+json(;.*)?");
-    private static final Pattern COMMON_PREFIX_ENUM_NAME = Pattern.compile("[a-zA-Z0-9]+\\z");
-    /** Matches a trailing run of digits at the end of a name, used by {@link #generateNextName}. */
-    private static final Pattern TRAILING_DIGITS = Pattern.compile("\\d+\\z");
-    /**
-     * Cache of removeCharRegEx string → compiled {@link Pattern} with {@link Pattern#UNICODE_CHARACTER_CLASS}.
-     * {@code sanitizeName} is called once per unique (name, regex, exceptions) tuple, so the regex string
-     * (almost always {@code "\\W"}) would otherwise be recompiled for every unique property/model name.
-     */
-    private static final ConcurrentHashMap<String, Pattern> REMOVE_CHAR_UNICODE_PATTERN_CACHE = new ConcurrentHashMap<>();
+
+    // --- HTTP / path patterns ---
+    protected static final Pattern STARTS_WITH_SLASH = Pattern.compile("^/.*");
+    protected static final Pattern UNESCAPED_SLASH = Pattern.compile("(?<!\\\\)/");
+    protected static final Pattern LEFT_CURLY_BRACE = Pattern.compile("\\{");
+    protected static final Pattern RIGHT_CURLY_BRACE = Pattern.compile("}");
+    protected static final Pattern PATH_PARAMETER = Pattern.compile("\\{([^}]+)}");
+    /** Matches a path segment that is entirely a parameter placeholder, e.g. {@code {id}}. */
+    protected static final Pattern IS_PATH_PARAM = Pattern.compile("^\\{.*}$");
+    /**
+     * Matches a callback path-expression parameter like {@code {$request.body#/id}}.
+     */
+    protected static final Pattern CALLBACK_EXPRESSION_PARAM = Pattern.compile("\\{\\$.*}");
+    /** Matches a 2xx HTTP success status code (e.g. {@code 200}, {@code 201}). */
+    protected static final Pattern HTTP_2XX_CODE = Pattern.compile("2[0-9][0-9]");
+
+    // --- Whitespace & line-ending patterns ---
+    protected static final Pattern NEWLINE = Pattern.compile("\n");
+    protected static final Pattern TRAILING_NEWLINE = Pattern.compile("\n$");
+    protected static final Pattern WHITESPACE = Pattern.compile("\\s+");
+    /** Matches one or more trailing whitespace characters in an identifier. */
+    protected static final Pattern TRAILING_WHITESPACE = Pattern.compile("\\s+$");
+    /** Matches any string that ends with at least one whitespace character. */
+    protected static final Pattern ENDS_WITH_WHITESPACE = Pattern.compile(".*\\s$");
+    /**
+     * Matches tab, newline, or carriage-return; used in {@link #escapeText}.
+     */
+    protected static final Pattern CONTROL_WHITESPACE = Pattern.compile("[\\t\\n\\r]");
+    protected static final Pattern MULTILINE_STRING = Pattern.compile("\r\n|\r|\n");
+    /** Splits on semicolon or new line, ignoring surrounding whitespace. */
+    protected static final Pattern SPLIT_ON_SEMICOLON_OR_NEWLINE_REGEX = Pattern.compile("\\s*(;|\\r?\\n)\\s*");
+    /** Splits on line-endings, both Windows ({@code \r\n}) and Unix ({@code \n}). */
+    public static final Pattern SPLIT_ON_NEWLINE = Pattern.compile("\\r?\\n");
+
+    // --- Underscore patterns ---
+    protected static final Pattern LEADING_UNDERSCORES = Pattern.compile("^_*");
+    protected static final Pattern MULTI_UNDERSCORES = Pattern.compile("_+");
+    protected static final Pattern MULTI_TRAILING_UNDERSCORES = Pattern.compile("_+$");
+    protected static final Pattern MULTI_LEADING_UNDERSCORES = Pattern.compile("^_+");
+    protected static final Pattern FIRST_LEADING_UNDERSCORE = Pattern.compile("^_");
+    protected static final Pattern LAST_TRAILING_UNDERSCORE = Pattern.compile("_$");
+
+    // --- Hyphen & separator patterns ---
+    protected static final Pattern MINUS = Pattern.compile("-");
+    /** Matches two or more consecutive hyphens. */
+    protected static final Pattern MULTI_HYPHEN = Pattern.compile("-{2,}");
+    /** Matches one or more leading hyphens (at start of string). */
+    protected static final Pattern LEADING_HYPHENS = Pattern.compile("^-+");
+    /** Matches one or more trailing hyphens (at end of string). */
+    protected static final Pattern TRAILING_HYPHENS = Pattern.compile("-+$");
+    protected static final Pattern PLUS = Pattern.compile("\\+");
+    protected static final Pattern DOT = Pattern.compile("\\.");
+    /** Matches {@code .}, {@code /}, or {@code \} — for package-name-to-path conversion. */
+    protected static final Pattern PACKAGE_SEPARATOR = Pattern.compile("[./\\\\]");
+    /** Splits on {@code  | } (the union-type pipe separator), e.g. {@code TypeA | TypeB}. */
+    protected static final Pattern SPLIT_ON_PIPE = Pattern.compile(" \\| ");
+    /** Splits on {@code |} used as a single-char separator in rule strings. */
+    protected static final Pattern SPLIT_ON_PIPE_CHAR = Pattern.compile("[|]");
+
+    // --- Identifier & name-sanitization patterns ---
+    /**
+     * Matches a string that starts with a digit (anchored); used across language generators.
+     */
+    protected static final Pattern STARTS_WITH_DIGIT = Pattern.compile("^\\d.*");
+    /**
+     * Matches a trailing run of digits at the end of a name, used by {@link #generateNextName}.
+     */
+    protected static final Pattern TRAILING_DIGITS = Pattern.compile("\\d+\\z");
+    /** Matches strings consisting entirely of ASCII digits. */
+    protected static final Pattern DIGITS_ONLY = Pattern.compile("^\\d+$");
+    /**
+     * Matches a string consisting entirely of uppercase letters and underscores.
+     */
+    protected static final Pattern ALL_UPPER_UNDERSCORE = Pattern.compile("^[A-Z_]*$");
+    /**
+     * Matches a string consisting entirely of uppercase letters, underscores, and digits.
+     */
+    protected static final Pattern ALL_UPPER_UNDERSCORE_DIGITS = Pattern.compile("^[A-Z0-9_]*$");
+    /** Matches the camelCase word boundary. */
+    protected static final Pattern CAMEL_CASE_BOUNDARY = Pattern.compile("([a-z0-9])([A-Z])");
+    /** Matches a CamelCase-initial type name like {@code FooBar} (used in Swift/Kotlin). */
+    protected static final Pattern CAMEL_INITIAL = Pattern.compile("[A-Z][a-z0-9]+[a-zA-Z0-9]*");
+    /**
+     * Matches one or more non-word characters; used in {@link #toEnumVarName} and {@link #sanitizeName}.
+     */
+    protected static final Pattern NON_WORD_PLUS = Pattern.compile("\\W+");
+    protected static final Pattern NON_WORD_CHAR = Pattern.compile("[^a-zA-Z0-9_]");
+    /** Matches one or more characters that are not ASCII alphanumeric (no underscore). */
+    protected static final Pattern NON_ALPHANUMERIC = Pattern.compile("[^a-zA-Z0-9]+");
+    /** Matches exactly one character that is not ASCII alphanumeric (no underscore). */
+    protected static final Pattern NON_ALPHANUMERIC_CHAR = Pattern.compile("[^a-zA-Z0-9]");
+    protected static final Pattern DASH_UNDERSCORE_SPACE_COLON_PARENTHESES = Pattern.compile("[-_ :()]");
+    protected static final Pattern COMMON_PREFIX_ENUM_NAME = Pattern.compile("[a-zA-Z0-9]+\\z");
+
+    // --- String literal & escaping patterns ---
+    protected static final Pattern TRAILING_BACKSLASHES = Pattern.compile("\\\\+$");
+    protected static final Pattern ENCLOSING_QUOTES = Pattern.compile("^\"|\"$");
 
     /**
      * True if the code generator supports multiple class inheritance.
@@ -957,12 +1044,12 @@ public String toEnumValue(String value, String datatype) {
      * @return the sanitized variable name for enum
      */
     public String toEnumVarName(String value, String datatype) {
-        if (value.length() == 0) {
+        if (value.isEmpty()) {
             return "EMPTY";
         }
 
-        String var = value.replaceAll("\\W+", "_").toUpperCase(Locale.ROOT);
-        if (var.matches("\\d.*")) {
+        String var = NON_WORD_PLUS.matcher(value).replaceAll("_").toUpperCase(Locale.ROOT);
+        if (STARTS_WITH_DIGIT.matcher(var).matches()) {
             var = "_" + var;
         }
 
@@ -981,8 +1068,8 @@ public boolean specVersionGreaterThanOrEqualTo310(OpenAPI openAPI) {
         } else {
             originalSpecVersion = openAPI.getOpenapi();
         }
-        Integer specMajorVersion = Integer.parseInt(originalSpecVersion.substring(0, 1));
-        Integer specMinorVersion = Integer.parseInt(originalSpecVersion.substring(2, 3));
+        int specMajorVersion = Integer.parseInt(originalSpecVersion.substring(0, 1));
+        int specMinorVersion = Integer.parseInt(originalSpecVersion.substring(2, 3));
         return specMajorVersion == 3 && specMinorVersion >= 1;
     }
 
@@ -1172,11 +1259,10 @@ public String escapeText(String input) {
         // replace " with \"
         // outer unescape to retain the original multi-byte characters
         // finally escalate characters avoiding code injection
+        String unescaped = StringEscapeUtils.unescapeJava(
+                StringEscapeUtils.escapeJava(input).replace("\\/", "/"));
         return escapeUnsafeCharacters(
-                StringEscapeUtils.unescapeJava(
-                                StringEscapeUtils.escapeJava(input)
-                                        .replace("\\/", "/"))
-                        .replaceAll("[\\t\\n\\r]", " ")
+                CONTROL_WHITESPACE.matcher(unescaped).replaceAll(" ")
                         .replace("\\", "\\\\")
                         .replace("\"", "\\\""));
     }
@@ -1216,7 +1302,7 @@ public String escapeTextWhileAllowingNewLines(String input) {
                 StringEscapeUtils.unescapeJava(
                                 StringEscapeUtils.escapeJava(input)
                                         .replace("\\/", "/"))
-                        .replaceAll("\\t", " ")
+                        .replace("\t", " ")
                         .replace("\\", "\\\\")
                         .replace("\"", "\\\""));
     }
@@ -4360,7 +4446,7 @@ void updateDefaultToEmptyContainer(CodegenProperty cp, Schema p) {
      * @param input a set of rules separated by `|`
      */
     void parseDefaultToEmptyContainer(String input) {
-        String[] inputs = input.split("[|]");
+        String[] inputs = SPLIT_ON_PIPE_CHAR.split(input);
         String containerType;
         for (String rule : inputs) {
             if (StringUtils.isEmpty(rule)) {
@@ -5261,7 +5347,7 @@ public CodegenCallback fromCallback(String name, Callback callback, List<Server>
                         } else {
                             boolean genId = op.getOperationId() == null;
                             if (genId) {
-                                op.setOperationId(getOrGenerateOperationId(op, c.name + "_" + expression.replaceAll("\\{\\$.*}", ""), method));
+                                op.setOperationId(getOrGenerateOperationId(op, c.name + "_" + CALLBACK_EXPRESSION_PARAM.matcher(expression).replaceAll(""), method));
                             }
 
                             if (op.getExtensions() == null) {
@@ -5833,8 +5919,8 @@ protected String getOrGenerateOperationId(Operation operation, String path, Stri
 
         if (StringUtils.isBlank(operationId)) {
             String tmpPath = path;
-            tmpPath = tmpPath.replaceAll("\\{", "");
-            tmpPath = tmpPath.replaceAll("\\}", "");
+            tmpPath = tmpPath.replace("{", "");
+            tmpPath = tmpPath.replace("}", "");
             String[] parts = (tmpPath + "/" + httpMethod).split("/");
             StringBuilder builder = new StringBuilder();
             if ("/".equals(tmpPath)) {
@@ -5862,7 +5948,7 @@ protected String getOrGenerateOperationId(Operation operation, String path, Stri
         // remove prefix in operationId
         if (removeOperationIdPrefix) {
             // The prefix is everything before the removeOperationIdPrefixCount occurrence of removeOperationIdPrefixDelimiter
-            String[] components = operationId.split("[" + removeOperationIdPrefixDelimiter + "]");
+            String[] components = PatternCache.get("[" + removeOperationIdPrefixDelimiter + "]").split(operationId);
             if (components.length > 1) {
                 // If removeOperationIdPrefixCount is -1 or bigger that the number of occurrences, uses the last one
                 int component_number = removeOperationIdPrefixCount == -1 ? components.length - 1 : removeOperationIdPrefixCount;
@@ -6757,15 +6843,13 @@ public String sanitizeName(final String name, String removeCharRegEx, ArrayList<
 
             // /api/films/get => _api_films_get
             // \api\films\get => _api_films_get
-            modifiable = modifiable.replaceAll("/", "_");
-            modifiable = modifiable.replaceAll("\\\\", "_");
+            modifiable = modifiable.replace("/", "_");
+            modifiable = modifiable.replace("\\", "_");
 
             // remove everything else other than word, number and _
             // $php_variable => php_variable
             if (allowUnicodeIdentifiers) { //could be converted to a single line with ?: operator
-                modifiable = REMOVE_CHAR_UNICODE_PATTERN_CACHE
-                        .computeIfAbsent(sanitizeNameOptions.getRemoveCharRegEx(),
-                                regex -> Pattern.compile(regex, Pattern.UNICODE_CHARACTER_CLASS))
+                modifiable = PatternCache.get(sanitizeNameOptions.getRemoveCharRegEx(), Pattern.UNICODE_CHARACTER_CLASS)
                         .matcher(modifiable).replaceAll("");
             } else {
                 modifiable = modifiable.replaceAll(sanitizeNameOptions.getRemoveCharRegEx(), "");
@@ -6792,7 +6876,7 @@ public String sanitizeTag(String tag) {
         tag = camelize(sanitizeName(tag));
 
         // tag starts with numbers
-        if (tag.matches("^\\d.*")) {
+        if (STARTS_WITH_DIGIT.matcher(tag).matches()) {
             tag = "Class" + tag;
         }
 
@@ -7053,8 +7137,8 @@ public String addRegularExpressionDelimiter(String pattern) {
             return pattern;
         }
 
-        if (!pattern.matches("^/.*")) {
-            return "/" + pattern.replaceAll("/", "\\\\/") + "/";
+        if (!pattern.startsWith("/")) {
+            return "/" + pattern.replace("/", "\\/") + "/";
         }
 
         return pattern;
@@ -7704,7 +7788,7 @@ protected void addBodyModelSchema(CodegenParameter codegenParameter, String name
 
             if (codegenProperty != null && codegenProperty.getComplexType() != null && codegenProperty.getComplexType().contains(" | ")) {
                 // TODO move this splitting logic to the generator that needs it only
-                List<String> parts = Arrays.asList(codegenProperty.getComplexType().split(" \\| "));
+                List<String> parts = Arrays.asList(SPLIT_ON_PIPE.split(codegenProperty.getComplexType()));
                 imports.addAll(parts);
 
                 String codegenModelName = codegenProperty.getComplexType();
diff --git a/modules/openapi-generator/src/main/java/org/openapitools/codegen/DefaultGenerator.java b/modules/openapi-generator/src/main/java/org/openapitools/codegen/DefaultGenerator.java
index 0fa4b0dceea5..588bb27523df 100644
--- a/modules/openapi-generator/src/main/java/org/openapitools/codegen/DefaultGenerator.java
+++ b/modules/openapi-generator/src/main/java/org/openapitools/codegen/DefaultGenerator.java
@@ -1435,7 +1435,7 @@ protected File processTemplateToFile(Map<String, Object> templateData, String te
     private final Set<String> seenFilesLower = new HashSet<>();
 
     private File processTemplateToFile(Map<String, Object> templateData, String templateName, String outputFilename, boolean shouldGenerate, String skippedByOption, String intendedOutputDir) throws IOException {
-        String adjustedOutputFilename = outputFilename.replaceAll("//", "/").replace('/', File.separatorChar);
+        String adjustedOutputFilename = outputFilename.replace("//", "/").replace('/', File.separatorChar);
         File target = new File(adjustedOutputFilename);
         if (ignoreProcessor.allowsFile(target)) {
             if (shouldGenerate) {
diff --git a/modules/openapi-generator/src/main/java/org/openapitools/codegen/InlineModelResolver.java b/modules/openapi-generator/src/main/java/org/openapitools/codegen/InlineModelResolver.java
index 777fed9b2cb4..e9ee7b64de0d 100644
--- a/modules/openapi-generator/src/main/java/org/openapitools/codegen/InlineModelResolver.java
+++ b/modules/openapi-generator/src/main/java/org/openapitools/codegen/InlineModelResolver.java
@@ -37,8 +37,11 @@
 import org.slf4j.LoggerFactory;
 
 import java.util.*;
+import java.util.regex.Pattern;
 
 public class InlineModelResolver {
+    private static final Pattern LEADING_DIGIT     = Pattern.compile("^[0-9]");
+    private static final Pattern NON_ALPHANUMERIC  = Pattern.compile("[^A-Za-z0-9]");
     private OpenAPI openAPI;
     private Map<String, Schema> addedModels = new HashMap<>();
     private Map<String, String> generatedSignature = new HashMap<>();
@@ -785,9 +788,9 @@ private void addGenerated(String name, Schema model) {
      * @param name name to be processed to make sure it's sanitized
      */
     private String sanitizeName(final String name) {
-        return name
-                .replaceAll("^[0-9]", "_$0") // e.g. 12object => _12object
-                .replaceAll("[^A-Za-z0-9]", "_"); // e.g. io.schema.User name => io_schema_User_name
+        return NON_ALPHANUMERIC.matcher(
+                LEADING_DIGIT.matcher(name).replaceFirst("_$0")) // e.g. 12object => _12object
+                .replaceAll("_"); // e.g. io.schema.User name => io_schema_User_name
     }
 
     /**
diff --git a/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/AbstractAdaCodegen.java b/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/AbstractAdaCodegen.java
index 4762205e7e1b..0b196dd03377 100644
--- a/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/AbstractAdaCodegen.java
+++ b/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/AbstractAdaCodegen.java
@@ -38,6 +38,7 @@
 
 import java.io.File;
 import java.util.*;
+import java.util.regex.Pattern;
 
 import static org.openapitools.codegen.utils.CamelizeOption.LOWERCASE_FIRST_LETTER;
 import static org.openapitools.codegen.utils.StringUtils.camelize;
@@ -398,7 +399,7 @@ public String toModelName(final String name) {
         }
 
         // model name starts with number
-        if (result.matches("^\\d.*")) {
+        if (STARTS_WITH_DIGIT.matcher(result).matches()) {
             String modelName = "Model_" + result; // e.g. 200Response => Model_200Response (after camelize)
             LOGGER.warn("{} (model name starts with number) cannot be used as model name. Renamed to {}", name,
                     modelName);
@@ -439,16 +440,16 @@ else if (getSymbolName(value) != null) {
         else if ("Integer".equals(datatype) || "Long".equals(datatype) ||
                 "Float".equals(datatype) || "Double".equals(datatype)) {
             String varName = "NUMBER_" + value;
-            varName = varName.replaceAll("-", "MINUS_");
-            varName = varName.replaceAll("\\+", "PLUS_");
-            varName = varName.replaceAll("\\.", "_DOT_");
+            varName = varName.replace("-", "MINUS_");
+            varName = varName.replace("+", "PLUS_");
+            varName = varName.replace(".", "_DOT_");
             var = varName;
         }
 
         // string
         else {
-            var = value.replaceAll("\\W+", "_").toUpperCase(Locale.ROOT);
-            if (var.matches("\\d.*")) {
+            var = NON_WORD_PLUS.matcher(value).replaceAll("_").toUpperCase(Locale.ROOT);
+            if (STARTS_WITH_DIGIT.matcher(var).matches()) {
                 var = "_" + var;
             } else {
                 var = sanitizeName(var);
@@ -1094,7 +1095,7 @@ private List<CodegenSecurity> postProcessAuthMethod(List<CodegenSecurity> authMe
                                 ident = name;
                             }
                             scopeIndex++;
-                            ident = toAdaIdentifier(sanitizeName(ident.replaceAll(":", "_")), "S_");
+                            ident = toAdaIdentifier(sanitizeName(ident.replace(":", "_")), "S_");
                             if (operationsScopes.containsValue(ident)) {
                                 ident = ident + "_" + scopeIndex;
                             }
diff --git a/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/AbstractApexCodegen.java b/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/AbstractApexCodegen.java
index 6a090df03d5a..ad0f2675e59b 100644
--- a/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/AbstractApexCodegen.java
+++ b/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/AbstractApexCodegen.java
@@ -32,6 +32,7 @@
 import org.slf4j.LoggerFactory;
 
 import java.util.*;
+import java.util.regex.Pattern;
 
 import static org.openapitools.codegen.utils.CamelizeOption.LOWERCASE_FIRST_LETTER;
 import static org.openapitools.codegen.utils.StringUtils.camelize;
@@ -39,7 +40,17 @@
 public abstract class AbstractApexCodegen extends DefaultCodegen implements CodegenConfig {
     private final Logger LOGGER = LoggerFactory.getLogger(AbstractApexCodegen.class);
 
-    @Setter protected Boolean serializableModel = false;
+    private static final Pattern DATE_FORMAT = Pattern.compile("^\\d{4}(-\\d{2}){2}");
+    private static final Pattern DATETIME_FORMAT = Pattern.compile("^\\d{4}([-T:]\\d{2}){5}.+");
+    private static final Pattern NON_NUMERIC = Pattern.compile("[^-0-9.]");
+    private static final Pattern UNSAFE_PACKAGE_CHARS = Pattern.compile("[^a-zA-Z0-9_.]");
+    private static final Pattern INTEGER_PATTERN = Pattern.compile("^-?\\d+$");
+    private static final Pattern UNDERSCORE_CLASS = Pattern.compile("^_*class$");
+    private static final Pattern DATE_SEP_ZERO = Pattern.compile("-0?");
+    private static final Pattern DATETIME_SEP_ZERO = Pattern.compile("[-T:]0?");
+
+    @Setter
+    protected Boolean serializableModel = false;
 
     public AbstractApexCodegen() {
         super();
@@ -77,11 +88,9 @@ public String escapeReservedWord(String name) {
     public String sanitizeName(String name) {
         name = super.sanitizeName(name);
         if (name.contains("__")) { // Preventing namespacing
-            name = name.replaceAll("__", "_");
-        }
-        if (name.matches("^\\d.*")) {  // Prevent named credentials with leading number
-            name = name.replaceAll("^\\d.*", "");
+            name = name.replace("__", "_");
         }
+        name = STARTS_WITH_DIGIT.matcher(name).replaceAll(""); // Prevent named credentials with leading number
         return name;
     }
 
@@ -90,7 +99,7 @@ public String toVarName(String name) {
         // sanitize name
         name = sanitizeName(name); // FIXME: a parameter should not be assigned. Also declare the methods parameters as 'final'.
 
-        if (name.toLowerCase(Locale.ROOT).matches("^_*class$")) {
+        if (UNDERSCORE_CLASS.matcher(name.toLowerCase(Locale.ROOT)).matches()) {
             return "propertyClass";
         }
 
@@ -99,7 +108,7 @@ public String toVarName(String name) {
         }
 
         // if it's all upper case, do nothing
-        if (name.matches("^[A-Z_]*$")) {
+        if (ALL_UPPER_UNDERSCORE.matcher(name).matches()) {
             if (isReservedWord(name)) {
                 name = escapeReservedWord(name);
             }
@@ -115,7 +124,7 @@ public String toVarName(String name) {
         name = camelize(name, LOWERCASE_FIRST_LETTER);
 
         // for reserved word or word starting with number, append _
-        if (isReservedWord(name) || name.matches("^\\d.*")) {
+        if (isReservedWord(name) || STARTS_WITH_DIGIT.matcher(name).matches()) {
             name = escapeReservedWord(name);
         }
 
@@ -169,7 +178,7 @@ public String toModelName(final String name) {
         }
 
         // model name starts with number
-        if (camelizedName.matches("^\\d.*")) {
+        if (STARTS_WITH_DIGIT.matcher(camelizedName).matches()) {
             final String modelName = "Model" + camelizedName; // e.g. 200Response => Model200Response (after camelize)
             LOGGER.warn("{} (model name starts with number) cannot be used as model name. Renamed to {}", name,
                     modelName);
@@ -318,8 +327,8 @@ public String toExampleValue(Schema p) {
             p.setExample(example);
             example = "EncodingUtil.base64Decode('" + example + "')";
         } else if (ModelUtils.isDateSchema(p)) {
-            if (example.matches("^\\d{4}(-\\d{2}){2}")) {
-                example = example.substring(0, 10).replaceAll("-0?", ", ");
+            if (DATE_FORMAT.matcher(example).find()) {
+                example = DATE_SEP_ZERO.matcher(example.substring(0, 10)).replaceAll(", ");
             } else if (example.isEmpty()) {
                 example = "2000, 1, 23";
             } else {
@@ -329,8 +338,8 @@ public String toExampleValue(Schema p) {
             }
             example = "Date.newInstance(" + example + ")";
         } else if (ModelUtils.isDateTimeSchema(p)) {
-            if (example.matches("^\\d{4}([-T:]\\d{2}){5}.+")) {
-                example = example.substring(0, 19).replaceAll("[-T:]0?", ", ");
+            if (DATETIME_FORMAT.matcher(example).find()) {
+                example = DATETIME_SEP_ZERO.matcher(example.substring(0, 19)).replaceAll(", ");
             } else if (example.isEmpty()) {
                 example = "2000, 1, 23, 4, 56, 7";
             } else {
@@ -340,7 +349,7 @@ public String toExampleValue(Schema p) {
             }
             example = "Datetime.newInstanceGmt(" + example + ")";
         } else if (ModelUtils.isNumberSchema(p)) {
-            example = example.replaceAll("[^-0-9.]", "");
+            example = NON_NUMERIC.matcher(example).replaceAll("");
             example = example.isEmpty() ? "1.3579" : example;
         } else if (ModelUtils.isFileSchema(p)) {
             if (example.isEmpty()) {
@@ -380,7 +389,7 @@ public String toExampleValue(Schema p) {
                     ? "'046b6c7f-0b8a-43b9-b35d-6489e6daee91'"
                     : "'" + escapeText(example) + "'";
         } else if (ModelUtils.isIntegerSchema(p)) {
-            example = example.matches("^-?\\d+$") ? example : "0";
+            example = INTEGER_PATTERN.matcher(example).matches() ? example : "0";
         } else if (ModelUtils.isObjectSchema(p)) {
             example = example.isEmpty() ? "null" : example;
         } else {
@@ -524,15 +533,15 @@ public String toEnumVarName(String value, String datatype) {
         if ("Integer".equals(datatype) || "Long".equals(datatype) ||
                 "Float".equals(datatype) || "Double".equals(datatype)) {
             String varName = "NUMBER_" + value;
-            varName = varName.replaceAll("-", "MINUS_");
-            varName = varName.replaceAll("\\+", "PLUS_");
-            varName = varName.replaceAll("\\.", "_DOT_");
+            varName = varName.replace("-", "MINUS_");
+            varName = varName.replace("+", "PLUS_");
+            varName = varName.replace(".", "_DOT_");
             return varName;
         }
 
         // string
-        String var = value.replaceAll("\\W+", "_").toUpperCase(Locale.ROOT);
-        if (var.matches("\\d.*")) {
+        String var = NON_WORD_PLUS.matcher(value).replaceAll("_").toUpperCase(Locale.ROOT);
+        if (STARTS_WITH_DIGIT.matcher(var).matches()) {
             return "_" + var;
         } else {
             return var;
@@ -618,7 +627,7 @@ private static CodegenModel reconcileInlineEnums(CodegenModel codegenModel, Code
 
     private static String sanitizePackageName(String packageName) {
         packageName = packageName.trim(); // FIXME: a parameter should not be assigned. Also declare the methods parameters as 'final'.
-        packageName = packageName.replaceAll("[^a-zA-Z0-9_\\.]", "_");
+        packageName = UNSAFE_PACKAGE_CHARS.matcher(packageName).replaceAll("_");
         if (Strings.isNullOrEmpty(packageName)) {
             return "invalidPackageName";
         }
@@ -628,7 +637,7 @@ private static String sanitizePackageName(String packageName) {
 
     private String sanitizePath(String p) {
         //prefer replace a ", instead of a fuLL URL encode for readability
-        return p.replaceAll("\"", "%22");
+        return p.replace("\"", "%22");
     }
 
     @Override
diff --git a/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/AbstractCSharpCodegen.java b/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/AbstractCSharpCodegen.java
index ec07161ff199..7ab80bf0deae 100644
--- a/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/AbstractCSharpCodegen.java
+++ b/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/AbstractCSharpCodegen.java
@@ -54,6 +54,10 @@
 
 public abstract class AbstractCSharpCodegen extends DefaultCodegen {
 
+    /** Matches a regex literal that carries modifier flags after the closing slash, e.g. {@code /foo/i}. */
+    private static final Pattern HAS_MODIFIERS = Pattern.compile(".*/[gmiyuvsdlnx]+$");
+    private static final Pattern UNESCAPED_DOUBLE_QUOTE = Pattern.compile("(?<!\\\\)\"");
+
     protected boolean optionalAssemblyInfoFlag = true;
     protected boolean optionalEmitDefaultValuesFlag = false;
     protected boolean conditionalSerialization = false;
@@ -1420,7 +1424,7 @@ public String toOperationId(String operationId) {
         }
 
         // operationId starts with a number
-        if (operationId.matches("^\\d.*")) {
+        if (STARTS_WITH_DIGIT.matcher(operationId).find()) {
             LOGGER.warn("{} (starting with a number) cannot be used as method name. Renamed to {}", operationId, camelize(sanitizeName("call_" + operationId)));
             operationId = "call_" + operationId;
         }
@@ -1439,7 +1443,7 @@ public String toVarName(String name) {
         name = sanitizeName(name);
 
         // if it's all upper case, do nothing
-        if (name.matches("^[A-Z_]*$")) {
+        if (ALL_UPPER_UNDERSCORE.matcher(name).matches()) {
             return name;
         }
 
@@ -1448,7 +1452,7 @@ public String toVarName(String name) {
         name = camelize(name);
 
         // for reserved word or word starting with number, append _
-        if (isReservedWord(name) || name.matches("^\\d.*")) {
+        if (isReservedWord(name) || STARTS_WITH_DIGIT.matcher(name).find()) {
             name = escapeReservedWord(name);
         }
 
@@ -1470,10 +1474,10 @@ public String toParamName(String name) {
         name = sanitizeName(name);
 
         // replace - with _ e.g. created-at => created_at
-        name = name.replaceAll("-", "_");
+        name = name.replace("-", "_");
 
         // if it's all upper case, do nothing
-        if (name.matches("^[A-Z_]*$")) {
+        if (ALL_UPPER_UNDERSCORE.matcher(name).matches()) {
             return name;
         }
 
@@ -1495,7 +1499,7 @@ public String escapeReservedWord(CodegenModel model, String name) {
     @Override
     public String escapeReservedWord(String name) {
         if (isReservedWord(name) ||
-                name.matches("^\\d.*")) {
+                STARTS_WITH_DIGIT.matcher(name).find()) {
             name = AbstractCSharpCodegen.invalidParameterNamePrefix + camelize(name);
         }
         return name;
@@ -1673,7 +1677,7 @@ public String toModelName(String name) {
         }
 
         // model name starts with number
-        if (name.matches("^\\d.*")) {
+        if (STARTS_WITH_DIGIT.matcher(name).find()) {
             LOGGER.warn("{} (model name starts with number) cannot be used as model name. Renamed to {}", name,
                     camelize("model_" + name));
             name = camelize("model_" + name); // e.g. 200Response => Model200Response (after camelize)
@@ -1768,11 +1772,11 @@ public String toEnumValue(String value, String datatype) {
             return value;
         }
 
-        final String partiallyEscaped = value
+        final String partiallyEscaped = UNESCAPED_DOUBLE_QUOTE.matcher(value
                 .replace("\n", "\\n")
                 .replace("\t", "\\t")
-                .replace("\r", "\\r")
-                .replaceAll("(?<!\\\\)\"", "\\\\\"");
+                .replace("\r", "\\r"))
+                .replaceAll("\\\\\"");
 
         return escapeUnsafeCharacters(partiallyEscaped);
     }
@@ -1794,12 +1798,12 @@ public String toEnumVarName(String name, String datatype) {
 
         String enumName = sanitizeName(name);
 
-        enumName = enumName.replaceFirst("^_", "");
-        enumName = enumName.replaceFirst("_$", "");
+        enumName = FIRST_LEADING_UNDERSCORE.matcher(enumName).replaceFirst("");
+        enumName = LAST_TRAILING_UNDERSCORE.matcher(enumName).replaceFirst("");
 
         enumName = adjustNamingStyle(enumName) + this.enumValueSuffix;
 
-        if (enumName.matches("\\d.*")) { // starts with number
+        if (STARTS_WITH_DIGIT.matcher(enumName).find()) { // starts with number
             return "_" + enumName;
         } else {
             return enumName;
@@ -2039,9 +2043,7 @@ public void postProcessPattern(String pattern, Map<String, Object> vendorExtensi
             // gmiyuvsd - ecma modifiers
             // l - legacy modifier provided by this library, provides a way to opt out of culture invariant
             // nx - c# modifiers https://learn.microsoft.com/en-us/dotnet/standard/base-types/regular-expression-options
-            Pattern hasModifiers = Pattern.compile(".*/[gmiyuvsdlnx]+$");
-
-            int end = hasModifiers.matcher(pattern).find()
+            int end = HAS_MODIFIERS.matcher(pattern).find()
                     ? pattern.lastIndexOf('/')
                     : pattern.length() - 1;
 
@@ -2091,7 +2093,7 @@ public String addRegularExpressionDelimiter(String pattern) {
             return pattern;
         }
 
-        if (!pattern.matches("^/.*")) {
+        if (!pattern.startsWith("/")) {
             return "/" + pattern + "/";
         }
 
diff --git a/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/AbstractCppCodegen.java b/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/AbstractCppCodegen.java
index 8950c1d4b761..8263c755da69 100644
--- a/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/AbstractCppCodegen.java
+++ b/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/AbstractCppCodegen.java
@@ -42,6 +42,7 @@
 abstract public class AbstractCppCodegen extends DefaultCodegen implements CodegenConfig {
     private final Logger LOGGER = LoggerFactory.getLogger(AbstractCppCodegen.class);
 
+
     protected static final String RESERVED_WORD_PREFIX_OPTION = "reservedWordPrefix";
     protected static final String RESERVED_WORD_PREFIX_DESC = "Prefix to prepend to reserved words in order to avoid conflicts";
     protected String reservedWordPrefix = "r_";
@@ -159,7 +160,7 @@ public AbstractCppCodegen() {
     @SuppressWarnings("static-method")
     public String sanitizeName(String name) {
         String sanitizedName = super.sanitizeName(name);
-        sanitizedName = sanitizedName.replaceAll("-", "");
+        sanitizedName = sanitizedName.replace("-", "");
         return sanitizedName;
     }
 
@@ -220,7 +221,7 @@ public String toVarName(String name) {
             return sanitizeName(name);
         }
 
-        if (isReservedWord(name) || name.matches("^\\d.*")) {
+        if (isReservedWord(name) || STARTS_WITH_DIGIT.matcher(name).matches()) {
             return escapeReservedWord(name);
         }
 
@@ -262,7 +263,7 @@ public String toParamName(String name) {
             return parameterNameMapping.get(name);
         }
 
-        if (isReservedWord(name) || name.matches("^\\d.*")) {
+        if (isReservedWord(name) || STARTS_WITH_DIGIT.matcher(name).matches()) {
             return escapeReservedWord(name);
         }
 
@@ -279,7 +280,7 @@ public CodegenProperty fromProperty(String name, Schema p, boolean required) {
         } else {
             nameInCamelCase = sanitizeName(nameInCamelCase);
         }
-        if (isReservedWord(nameInCamelCase) || nameInCamelCase.matches("^\\d.*")) {
+        if (isReservedWord(nameInCamelCase) || STARTS_WITH_DIGIT.matcher(nameInCamelCase).matches()) {
             nameInCamelCase = escapeReservedWord(nameInCamelCase);
         }
         property.nameInCamelCase = nameInCamelCase;
diff --git a/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/AbstractDartCodegen.java b/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/AbstractDartCodegen.java
index 4d7eb4dbe7c1..fd603b126f07 100644
--- a/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/AbstractDartCodegen.java
+++ b/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/AbstractDartCodegen.java
@@ -26,6 +26,7 @@
 import java.io.InputStreamReader;
 import java.nio.charset.StandardCharsets;
 import java.util.*;
+import java.util.regex.Pattern;
 import java.util.stream.Stream;
 
 import static org.openapitools.codegen.utils.CamelizeOption.LOWERCASE_FIRST_LETTER;
@@ -35,6 +36,8 @@ public abstract class AbstractDartCodegen extends DefaultCodegen {
 
     private final Logger LOGGER = LoggerFactory.getLogger(AbstractDartCodegen.class);
 
+    private static final Pattern STARTS_WITH_OPT_NEG_DIGIT = Pattern.compile("^-?\\d.*");
+
     protected static final List<String> DEFAULT_SUPPORTED_CONTENT_TYPES = Arrays.asList(
             "application/json", "application/x-www-form-urlencoded", "multipart/form-data");
 
@@ -413,10 +416,10 @@ public String toVarName(String name) {
         if (name.equals("_")) {
             return "underscore";
         }
-        name = name.replaceAll("^_", "");
+        name = FIRST_LEADING_UNDERSCORE.matcher(name).replaceAll("");
 
         // if it's all upper case, do nothing
-        if (name.matches("^[A-Z_]*$")) {
+        if (ALL_UPPER_UNDERSCORE.matcher(name).matches()) {
             return name;
         }
 
@@ -432,7 +435,7 @@ public String toVarName(String name) {
         // pet_id => petId
         name = camelize(name, LOWERCASE_FIRST_LETTER);
 
-        if (name.matches("^\\d.*")) {
+        if (STARTS_WITH_DIGIT.matcher(name).matches()) {
             name = "n" + name;
         }
 
@@ -496,7 +499,7 @@ public String toModelName(final String name) {
         }
 
         // model name starts with number
-        if (camelizedName.matches("^\\d.*")) {
+        if (STARTS_WITH_DIGIT.matcher(camelizedName).matches()) {
             final String modelName = "Model" + camelizedName; // e.g. 200Response => Model200Response (after camelize)
             LOGGER.warn("{} (model name starts with number) cannot be used as model name. Renamed to {}", name, modelName);
             return modelName;
@@ -874,7 +877,7 @@ public String toEnumVarName(String value, String datatype) {
         if (("number".equalsIgnoreCase(datatype) ||
                 "double".equalsIgnoreCase(datatype) ||
                 "int".equalsIgnoreCase(datatype)) &&
-                value.matches("^-?\\d.*")) {
+                STARTS_WITH_OPT_NEG_DIGIT.matcher(value).matches()) {
             // Only rename numeric values when the datatype is numeric
             // AND the name is not changed by enum extensions (matches a numeric value).
             boolean isNegative = value.startsWith("-");
@@ -907,7 +910,7 @@ public String toOperationId(String operationId) {
         }
 
         // operationId starts with a number
-        if (operationId.matches("^\\d.*")) {
+        if (STARTS_WITH_DIGIT.matcher(operationId).matches()) {
             String newOperationId = camelize("call_" + operationId, LOWERCASE_FIRST_LETTER);
             LOGGER.warn("{} (starting with a number) cannot be used as method name. Renamed to {}", operationId, newOperationId);
             operationId = newOperationId;
diff --git a/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/AbstractEiffelCodegen.java b/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/AbstractEiffelCodegen.java
index 83f3fac174f5..a68977d1e297 100644
--- a/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/AbstractEiffelCodegen.java
+++ b/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/AbstractEiffelCodegen.java
@@ -32,6 +32,7 @@
 import org.slf4j.LoggerFactory;
 
 import java.util.*;
+import java.util.regex.Pattern;
 
 import static org.openapitools.codegen.utils.CamelizeOption.LOWERCASE_FIRST_LETTER;
 import static org.openapitools.codegen.utils.StringUtils.camelize;
@@ -40,6 +41,8 @@
 public abstract class AbstractEiffelCodegen extends DefaultCodegen implements CodegenConfig {
     private final Logger LOGGER = LoggerFactory.getLogger(AbstractEiffelCodegen.class);
 
+    private static final Pattern UNCAMELIZE_UPPER = Pattern.compile("(.)(\\p{Upper})");
+
     private final Set<String> parentModels = new HashSet<>();
     private final Multimap<String, CodegenModel> childrenByParent = ArrayListMultimap.create();
 
@@ -126,7 +129,7 @@ public String escapeReservedWord(String name) {
         if (this.reservedWordsMappings().containsKey(name)) {
             return this.reservedWordsMappings().get(name);
         }
-        if (name.matches("^\\d.*")) {// prepend var_
+        if (STARTS_WITH_DIGIT.matcher(name).matches()) {// prepend var_
             return "var_" + name;
         }
         return "var_" + name;
@@ -135,10 +138,10 @@ public String escapeReservedWord(String name) {
     @Override
     public String toVarName(String name) {
         // replace - with _ e.g. created-at => created_at
-        name = sanitizeName(name.replaceAll("-", "_"));
+        name = sanitizeName(name.replace("-", "_"));
 
         // if it's all upper case, do nothing
-        if (name.matches("^[A-Z_]*$")) {
+        if (ALL_UPPER_UNDERSCORE.matcher(name).matches()) {
             return name;
         }
 
@@ -156,7 +159,7 @@ public String toVarName(String name) {
         }
 
         // for reserved word or word starting with number, append
-        if (name.matches("^\\d.*")) {
+        if (STARTS_WITH_DIGIT.matcher(name).matches()) {
             name = escapeReservedWord(name);
         }
 
@@ -201,7 +204,7 @@ public String toModelFilename(String name) {
         }
 
         // model name starts with number
-        if (name.matches("^\\d.*")) {
+        if (STARTS_WITH_DIGIT.matcher(name).matches()) {
             LOGGER.warn("{} (model name starts with number) cannot be used as model name. Renamed to {}", name,
                     "model_" + name);
             name = "model_" + name; // e.g. 200Response => Model200Response
@@ -221,7 +224,7 @@ public String toModelFilename(String name) {
     @Override
     public String toApiFilename(String name) {
         // replace - with _ e.g. created-at => created_at
-        name = name.replaceAll("-", "_"); // FIXME: a parameter should not be
+        name = name.replace("-", "_"); // FIXME: a parameter should not be
         // assigned. Also declare the
         // methods parameters as 'final'.
 
@@ -348,7 +351,7 @@ public String toOperationId(String operationId) {
         }
 
         // operationId starts with a number
-        if (operationId.matches("^\\d.*")) {
+        if (STARTS_WITH_DIGIT.matcher(operationId).matches()) {
             LOGGER.warn(operationId + " (starting with a number) cannot be used as method sname. Renamed to " + camelize("call_" + operationId), true);
             sanitizedOperationId = camelize("call_" + sanitizedOperationId, LOWERCASE_FIRST_LETTER);
         }
@@ -584,7 +587,7 @@ public String toInstantiationType(Schema p) {
     }
 
     public String unCamelize(String name) {
-        return name.replaceAll("(.)(\\p{Upper})", "$1_$2").toLowerCase(Locale.ROOT);
+        return UNCAMELIZE_UPPER.matcher(name).replaceAll("$1_$2").toLowerCase(Locale.ROOT);
     }
 
     public String toEiffelFeatureStyle(String operationId) {
diff --git a/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/AbstractFSharpCodegen.java b/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/AbstractFSharpCodegen.java
index 7ca5e99015c2..edfd064108a3 100644
--- a/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/AbstractFSharpCodegen.java
+++ b/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/AbstractFSharpCodegen.java
@@ -44,6 +44,9 @@
 
 public abstract class AbstractFSharpCodegen extends DefaultCodegen implements CodegenConfig {
 
+    // ...existing code...
+
+
     protected boolean optionalAssemblyInfoFlag = true;
     protected boolean optionalProjectFileFlag = true;
 
@@ -627,7 +630,7 @@ public String toOperationId(String operationId) {
         }
 
         // operationId starts with a number
-        if (operationId.matches("^\\d.*")) {
+        if (STARTS_WITH_DIGIT.matcher(operationId).matches()) {
             LOGGER.warn("{} (starting with a number) cannot be used as method name. Renamed to {}", operationId, camelize(sanitizeName("call_" + operationId)));
             operationId = "call_" + operationId;
         }
@@ -670,14 +673,14 @@ public String toVarName(String name) {
         name = sanitizeName(name);
 
         // if it's all upper case, do nothing
-        if (name.matches("^[A-Z_]*$")) {
+        if (ALL_UPPER_UNDERSCORE.matcher(name).matches()) {
             return name;
         }
 
         name = getNameUsingModelPropertyNaming(name);
 
         // for reserved word or word starting with number, append _
-        if (isReservedWord(name) || name.matches("^\\d.*")) {
+        if (isReservedWord(name) || STARTS_WITH_DIGIT.matcher(name).matches()) {
             name = escapeReservedWord(name);
         }
         return name;
@@ -689,10 +692,10 @@ public String toParamName(String name) {
         name = sanitizeName(name);
 
         // replace - with _ e.g. created-at => created_at
-        name = name.replaceAll("-", "_");
+        name = name.replace("-", "_");
 
         // if it's all upper case, do nothing
-        if (name.matches("^[A-Z_]*$")) {
+        if (ALL_UPPER_UNDERSCORE.matcher(name).matches()) {
             return name;
         }
 
@@ -701,7 +704,7 @@ public String toParamName(String name) {
         name = camelize(name, LOWERCASE_FIRST_LETTER);
 
         // for reserved word or word starting with number, append _
-        if (isReservedWord(name) || name.matches("^\\d.*")) {
+        if (isReservedWord(name) || STARTS_WITH_DIGIT.matcher(name).matches()) {
             name = escapeReservedWord(name);
         }
 
@@ -895,7 +898,7 @@ public String toModelName(String name) {
         }
 
         // model name starts with number
-        if (name.matches("^\\d.*")) {
+        if (STARTS_WITH_DIGIT.matcher(name).matches()) {
             LOGGER.warn("{} (model name starts with number) cannot be used as model name. Renamed to {}", name,
                     camelize("model_" + name));
             name = "model_" + name; // e.g. 200Response => Model200Response (after camelize)
@@ -959,12 +962,12 @@ public String toEnumVarName(String name, String datatype) {
 
         String enumName = sanitizeName(name);
 
-        enumName = enumName.replaceFirst("^_", "");
-        enumName = enumName.replaceFirst("_$", "");
+        enumName = FIRST_LEADING_UNDERSCORE.matcher(enumName).replaceFirst("");
+        enumName = LAST_TRAILING_UNDERSCORE.matcher(enumName).replaceFirst("");
 
         enumName = camelize(enumName) + "Enum";
 
-        if (enumName.matches("\\d.*")) { // starts with number
+        if (STARTS_WITH_DIGIT.matcher(enumName).matches()) { // starts with number
             return "_" + enumName;
         } else {
             return enumName;
diff --git a/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/AbstractGoCodegen.java b/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/AbstractGoCodegen.java
index 16b909eab448..bbbdaae36c8b 100644
--- a/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/AbstractGoCodegen.java
+++ b/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/AbstractGoCodegen.java
@@ -29,6 +29,7 @@
 
 import java.io.File;
 import java.util.*;
+import java.util.regex.Pattern;
 
 import static org.openapitools.codegen.utils.CamelizeOption.LOWERCASE_FIRST_LETTER;
 import static org.openapitools.codegen.utils.StringUtils.camelize;
@@ -39,6 +40,8 @@ public abstract class AbstractGoCodegen extends DefaultCodegen implements Codege
     private final Logger LOGGER = LoggerFactory.getLogger(AbstractGoCodegen.class);
     private static final String NUMERIC_ENUM_PREFIX = "_";
 
+    private static final Pattern LEADING_TRAILING_SLASH = Pattern.compile("^/|/$");
+
     @Setter
     protected boolean withGoCodegenComment = false;
     @Setter
@@ -213,7 +216,7 @@ public String toVarName(String name) {
         name = sanitizeName(name);
 
         // if it's all upper case, do nothing
-        if (name.matches("^[A-Z_]*$"))
+        if (ALL_UPPER_UNDERSCORE.matcher(name).matches())
             return name;
 
         // camelize (lower first character) the variable name
@@ -227,7 +230,7 @@ public String toVarName(String name) {
         }
 
         // for reserved word or word starting with number, append _
-        if (name.matches("^\\d.*"))
+        if (STARTS_WITH_DIGIT.matcher(name).matches())
             name = "Var" + name;
 
         if ("AdditionalProperties".equals(name)) {
@@ -332,7 +335,7 @@ public String toModel(String name, boolean doUnderscore) {
         }
 
         // model name starts with number
-        if (name.matches("^\\d.*")) {
+        if (STARTS_WITH_DIGIT.matcher(name).matches()) {
             LOGGER.warn("{} (model name starts with number) cannot be used as model name. Renamed to {}", name,
                     "model_" + name);
             name = "model_" + name; // e.g. 200Response => Model200Response (after camelize)
@@ -348,7 +351,7 @@ public String toModel(String name, boolean doUnderscore) {
     public String toApiFilename(String name) {
         final String apiName;
         // replace - with _ e.g. created-at => created_at
-        String api = name.replaceAll("-", "_");
+        String api = name.replace("-", "_");
         // e.g. PetApi.go => pet_api.go
         api = "api_" + underscore(api);
         if (isReservedFilename(api)) {
@@ -498,7 +501,7 @@ public String toOperationId(String operationId) {
         }
 
         // operationId starts with a number
-        if (sanitizedOperationId.matches("^\\d.*")) {
+        if (STARTS_WITH_DIGIT.matcher(sanitizedOperationId).matches()) {
             LOGGER.warn("{} (starting with a number) cannot be used as method name. Renamed to {}", operationId, camelize("call_" + sanitizedOperationId));
             sanitizedOperationId = "call_" + sanitizedOperationId;
         }
@@ -789,7 +792,7 @@ public ModelsMap postProcessModels(ModelsMap objs) {
 
                 if (cp.pattern != null) {
                     cp.vendorExtensions.put("x-go-custom-tag", "validate:\"regexp=" +
-                            cp.pattern.replace("\\", "\\\\").replaceAll("^/|/$", "") +
+                            LEADING_TRAILING_SLASH.matcher(cp.pattern.replace("\\", "\\\\")).replaceAll("") +
                             "\"");
                 }
 
@@ -931,9 +934,9 @@ public String toEnumVarName(String name, String datatype) {
         // number
         if (isNumberType(datatype)) {
             String varName = name;
-            varName = varName.replaceAll("-", "MINUS_");
-            varName = varName.replaceAll("\\+", "PLUS_");
-            varName = varName.replaceAll("\\.", "_DOT_");
+            varName = varName.replace("-", "MINUS_");
+            varName = varName.replace("+", "PLUS_");
+            varName = varName.replace(".", "_DOT_");
             return NUMERIC_ENUM_PREFIX + varName;
         }
 
@@ -944,12 +947,12 @@ public String toEnumVarName(String name, String datatype) {
 
         // string
         String enumName = sanitizeName(underscore(name).toUpperCase(Locale.ROOT));
-        enumName = enumName.replaceFirst("^_", "");
-        enumName = enumName.replaceFirst("_$", "");
+        enumName = FIRST_LEADING_UNDERSCORE.matcher(enumName).replaceFirst("");
+        enumName = LAST_TRAILING_UNDERSCORE.matcher(enumName).replaceFirst("");
 
         if (isReservedWord(enumName)) { // reserved word
             return escapeReservedWord(enumName);
-        } else if (enumName.matches("\\d.*")) { // starts with a number
+        } else if (STARTS_WITH_DIGIT.matcher(enumName).matches()) { // starts with a number
             return NUMERIC_ENUM_PREFIX + enumName;
         } else {
             return enumName;
@@ -967,7 +970,7 @@ public String toEnumName(CodegenProperty property) {
         // remove [] for array or map of enum
         enumName = enumName.replace("[]", "");
 
-        if (enumName.matches("\\d.*")) { // starts with number
+        if (STARTS_WITH_DIGIT.matcher(enumName).matches()) { // starts with number
             return NUMERIC_ENUM_PREFIX + enumName;
         } else {
             return enumName;
diff --git a/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/AbstractGraphQLCodegen.java b/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/AbstractGraphQLCodegen.java
index 0d383f375a61..261554a1b278 100644
--- a/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/AbstractGraphQLCodegen.java
+++ b/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/AbstractGraphQLCodegen.java
@@ -38,6 +38,7 @@ public abstract class AbstractGraphQLCodegen extends DefaultCodegen implements C
 
     private final Logger LOGGER = LoggerFactory.getLogger(AbstractGraphQLCodegen.class);
 
+
     protected String specFolder = "spec";
     @Setter protected String packageName = "openapi2graphql";
     @Setter protected String packageVersion = "1.0.0";
@@ -147,10 +148,10 @@ public String modelFileFolder() {
     @Override
     public String toVarName(String name) {
         // replace - with _ e.g. created-at => created_at
-        name = sanitizeName(name.replaceAll("-", "_"));
+        name = sanitizeName(name.replace("-", "_"));
 
         // if it's all upper case, do nothing
-        if (name.matches("^[A-Z_]*$"))
+        if (ALL_UPPER_UNDERSCORE.matcher(name).matches())
             return name;
 
         name = camelize(name, LOWERCASE_FIRST_LETTER);
@@ -160,7 +161,7 @@ public String toVarName(String name) {
             name = escapeReservedWord(name);
 
         // for reserved word or word starting with number, append _
-        if (name.matches("^\\d.*"))
+        if (STARTS_WITH_DIGIT.matcher(name).matches())
             name = camelize("var_" + name);
 
         return name;
@@ -195,7 +196,7 @@ public String toModelFilename(String name) {
         }
 
         // model name starts with number
-        if (name.matches("^\\d.*")) {
+        if (STARTS_WITH_DIGIT.matcher(name).matches()) {
             LOGGER.warn("{} (model name starts with number) cannot be used as model name. Renamed to {}", name,
                     "model_" + name);
             name = "model_" + name; // e.g. 200Response => Model200Response (after camelize)
@@ -207,7 +208,7 @@ public String toModelFilename(String name) {
     @Override
     public String toApiFilename(String name) {
         // replace - with _ e.g. created-at => created_at
-        name = name.replaceAll("-", "_"); // FIXME: a parameter should not be assigned. Also declare the methods parameters as 'final'.
+        name = name.replace("-", "_"); // FIXME: a parameter should not be assigned. Also declare the methods parameters as 'final'.
 
         // e.g. PetApi.graphql => pet_api.graphql
         return underscore(name) + "_api";
@@ -371,9 +372,9 @@ public String toEnumVarName(String name, String datatype) {
         // number
         if ("int".equals(datatype) || "double".equals(datatype) || "float".equals(datatype)) {
             String varName = name;
-            varName = varName.replaceAll("-", "MINUS_");
-            varName = varName.replaceAll("\\+", "PLUS_");
-            varName = varName.replaceAll("\\.", "_DOT_");
+            varName = varName.replace("-", "MINUS_");
+            varName = varName.replace("+", "PLUS_");
+            varName = varName.replace(".", "_DOT_");
             return varName;
         }
 
@@ -384,10 +385,10 @@ public String toEnumVarName(String name, String datatype) {
 
         // string
         String enumName = sanitizeName(underscore(name).toUpperCase(Locale.ROOT));
-        enumName = enumName.replaceFirst("^_", "");
-        enumName = enumName.replaceFirst("_$", "");
+        enumName = FIRST_LEADING_UNDERSCORE.matcher(enumName).replaceFirst("");
+        enumName = LAST_TRAILING_UNDERSCORE.matcher(enumName).replaceFirst("");
 
-        if (isReservedWord(enumName) || enumName.matches("\\d.*")) { // reserved word or starts with number
+        if (isReservedWord(enumName) || STARTS_WITH_DIGIT.matcher(enumName).matches()) { // reserved word or starts with number
             return escapeReservedWord(enumName);
         } else {
             return enumName;
@@ -401,7 +402,7 @@ public String toEnumName(CodegenProperty property) {
         // remove [] for array or map of enum
         enumName = enumName.replace("[]", "");
 
-        if (enumName.matches("\\d.*")) { // starts with number
+        if (STARTS_WITH_DIGIT.matcher(enumName).matches()) { // starts with number
             return "_" + enumName;
         } else {
             return enumName;
diff --git a/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/AbstractJavaCodegen.java b/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/AbstractJavaCodegen.java
index 58f7d0e1f226..f02e54d3ba51 100644
--- a/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/AbstractJavaCodegen.java
+++ b/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/AbstractJavaCodegen.java
@@ -83,6 +83,12 @@ public abstract class AbstractJavaCodegen extends DefaultCodegen implements Code
     private final Logger LOGGER = LoggerFactory.getLogger(AbstractJavaCodegen.class);
     private static final String ARTIFACT_VERSION_DEFAULT_VALUE = "1.0.0";
     private static final ZoneId UTC = ZoneId.of("UTC");
+    private static final Pattern LOMBOK_ANNOTATION = Pattern.compile("@lombok.(\\w+\\.)*(?<ClassName>\\w+)(\\(.*?\\))?");
+    private static final Pattern JAVA_UTIL_IMPORT = Pattern.compile("java\\.util\\.(List|ArrayList|Map|HashMap)");
+    private static final Pattern STARTS_WITH_UNDERSCORE_CLASS = Pattern.compile("^_*class$");
+    private static final Pattern ANNOTATION_IN_TYPE = Pattern.compile("(?:(?i)@[a-z0-9]*+([(].*[)]|\\s*))*+");
+    private static final Pattern NON_ALPHANUMERIC_UNICODE = Pattern.compile("\\P{Alnum}");
+    private static final Pattern INVALID_PACKAGE_CHARS = Pattern.compile("[^a-zA-Z0-9_.]");
 
     public static final String DEFAULT_LIBRARY = "<default>";
     public static final String DATE_LIBRARY = "dateLibrary";
@@ -452,10 +458,10 @@ public void processOpts() {
         convertPropertyToStringAndWriteBack(BOOLEAN_GETTER_PREFIX, this::setBooleanGetterPrefix);
         convertPropertyToBooleanAndWriteBack(IGNORE_ANYOF_IN_ENUM, this::setIgnoreAnyOfInEnum);
         convertPropertyToTypeAndWriteBack(ADDITIONAL_MODEL_TYPE_ANNOTATIONS,
-                annotations -> Arrays.asList(annotations.trim().split("\\s*(;|\\r?\\n)\\s*")),
+                annotations -> Arrays.asList(SPLIT_ON_SEMICOLON_OR_NEWLINE_REGEX.split(annotations.trim())),
                 this::setAdditionalModelTypeAnnotations);
         convertPropertyToTypeAndWriteBack(ADDITIONAL_ONE_OF_TYPE_ANNOTATIONS,
-                annotations -> Arrays.asList(annotations.trim().split("\\s*(;|\\r?\\n)\\s*")),
+                annotations -> Arrays.asList(SPLIT_ON_SEMICOLON_OR_NEWLINE_REGEX.split(annotations.trim())),
                 this::setAdditionalOneOfTypeAnnotations);
         convertPropertyToTypeAndWriteBack(ADDITIONAL_ENUM_TYPE_ANNOTATIONS,
                 annotations -> Arrays.asList(annotations.split(";")),
@@ -920,7 +926,7 @@ public String toVarName(String name) {
         // sanitize name
         name = sanitizeName(name, "\\W-[\\$]"); // FIXME: a parameter should not be assigned. Also declare the methods parameters as 'final'.
 
-        if (name.toLowerCase(Locale.ROOT).matches("^_*class$")) {
+        if (STARTS_WITH_UNDERSCORE_CLASS.matcher(name.toLowerCase(Locale.ROOT)).matches()) {
             return "propertyClass";
         }
 
@@ -929,12 +935,12 @@ public String toVarName(String name) {
         }
 
         // numbers are not allowed at the beginning
-        if (name.matches("^\\d.*")) {
+        if (STARTS_WITH_DIGIT.matcher(name).matches()) {
             name = "_" + name;
         }
 
         // if it's all upper case, do nothing
-        if (name.matches("^[A-Z0-9_]*$")) {
+        if (ALL_UPPER_UNDERSCORE_DIGITS.matcher(name).matches()) {
             return name;
         }
 
@@ -959,7 +965,7 @@ public String toVarName(String name) {
         }
 
         // for reserved word or word starting with number, append _
-        if (isReservedWord(name) || name.matches("^\\d.*")) {
+        if (isReservedWord(name) || STARTS_WITH_DIGIT.matcher(name).matches()) {
             name = escapeReservedWord(name);
         }
 
@@ -1035,7 +1041,7 @@ public String toModelName(final String name) {
         }
 
         // model name starts with number
-        if (camelizedName.matches("^\\d.*")) {
+        if (STARTS_WITH_DIGIT.matcher(camelizedName).matches()) {
             final String modelName = "Model" + camelizedName; // e.g. 200Response => Model200Response (after camelize)
             schemaKeyToModelNameCache.put(origName, modelName);
             LOGGER.warn("{} (model name starts with number) cannot be used as model name. Renamed to {}", name,
@@ -1209,10 +1215,10 @@ private String getStringBeanValidation(Schema<?> items) {
 
         if (StringUtils.isNotEmpty(items.getPattern())) {
             final String pattern = escapeUnsafeCharacters(
+                    CONTROL_WHITESPACE.matcher(
                     StringEscapeUtils.unescapeJava(
                                     StringEscapeUtils.escapeJava(items.getPattern())
-                                            .replace("\\/", "/"))
-                            .replaceAll("[\\t\\n\\r]", " ")
+                                            .replace("\\/", "/"))).replaceAll(" ")
                             .replace("\\", "\\\\")
                             .replace("\"", "\\\""));
 
@@ -1832,7 +1838,7 @@ public String toOperationId(String operationId) {
         }
 
         // operationId starts with a number
-        if (operationId.matches("^\\d.*")) {
+        if (STARTS_WITH_DIGIT.matcher(operationId).matches()) {
             LOGGER.warn(operationId + " (starting with a number) cannot be used as method name. Renamed to " + camelize("call_" + operationId), true);
             operationId = camelize("call_" + operationId, LOWERCASE_FIRST_LETTER);
         }
@@ -1983,7 +1989,7 @@ public void postProcessResponseWithProperty(CodegenResponse response, CodegenPro
      */
     public String removeAnnotations(String dataType) {
         if (dataType != null && dataType.contains("@")) {
-            return dataType.replaceAll("(?:(?i)@[a-z0-9]*+([(].*[)]|\\s*))*+", "");
+            return ANNOTATION_IN_TYPE.matcher(dataType).replaceAll("");
         }
         return dataType;
     }
@@ -1997,8 +2003,8 @@ public String removeAnnotations(String dataType) {
      */
     public String sanitizeDataType(String dataType) {
         String content = removeAnnotations(dataType);
-        if (content != null && content.matches(".*\\P{Alnum}.*")) {
-            content = content.replaceAll("\\P{Alnum}", "");
+        if (content != null && NON_ALPHANUMERIC_UNICODE.matcher(content).find()) {
+            content = NON_ALPHANUMERIC_UNICODE.matcher(content).replaceAll("");
         }
         return content;
     }
@@ -2084,10 +2090,8 @@ public ModelsMap postProcessModels(ModelsMap objs) {
 
         // parse lombok additional model type annotations
         Map<String, Boolean> lombokOptions = new HashMap<>();
-        String regexp = "@lombok.(\\w+\\.)*(?<ClassName>\\w+)(\\(.*?\\))?";
-        Pattern pattern = Pattern.compile(regexp);
         for (String annotation : additionalModelTypeAnnotations) {
-            Matcher matcher = pattern.matcher(annotation);
+            Matcher matcher = LOMBOK_ANNOTATION.matcher(annotation);
             if (matcher.find()) {
                 String className = matcher.group("ClassName");
                 lombokOptions.put(className, true);
@@ -2106,10 +2110,9 @@ public OperationsMap postProcessOperationsWithModels(OperationsMap objs, List<Mo
         // Remove imports of List, ArrayList, Map and HashMap as they are
         // imported in the template already.
         List<Map<String, String>> imports = objs.getImports();
-        Pattern pattern = Pattern.compile("java\\.util\\.(List|ArrayList|Map|HashMap)");
         for (Iterator<Map<String, String>> itr = imports.iterator(); itr.hasNext(); ) {
             String itrImport = itr.next().get("import");
-            if (pattern.matcher(itrImport).matches()) {
+            if (JAVA_UTIL_IMPORT.matcher(itrImport).matches()) {
                 itr.remove();
             }
         }
@@ -2253,9 +2256,9 @@ public String toEnumVarName(String value, String datatype) {
         if ("Integer".equals(datatype) || "Long".equals(datatype) ||
                 "Float".equals(datatype) || "Double".equals(datatype) || "BigDecimal".equals(datatype)) {
             String varName = "NUMBER_" + value;
-            varName = varName.replaceAll("-", "MINUS_");
-            varName = varName.replaceAll("\\+", "PLUS_");
-            varName = varName.replaceAll("\\.", "_DOT_");
+            varName = varName.replace("-", "MINUS_");
+            varName = varName.replace("+", "PLUS_");
+            varName = varName.replace(".", "_DOT_");
             return varName;
         }
 
@@ -2264,7 +2267,7 @@ public String toEnumVarName(String value, String datatype) {
         switch (getEnumPropertyNaming()) {
             case legacy:
                 // legacy ,e.g. WITHNUMBER1
-                var = value.replaceAll("\\W+", "_").toUpperCase(Locale.ROOT);
+                var = NON_WORD_PLUS.matcher(value).replaceAll("_").toUpperCase(Locale.ROOT);
                 break;
             case original:
                 // keep value as it is, if meets language naming convention
@@ -2277,10 +2280,10 @@ public String toEnumVarName(String value, String datatype) {
                 break;
             default:
                 // default to MACRO_CASE, e.g. WITH_NUMBER1
-                var = underscore(value.replaceAll("\\W+", "_")).toUpperCase(Locale.ROOT);
+                var = underscore(NON_WORD_PLUS.matcher(value).replaceAll("_")).toUpperCase(Locale.ROOT);
                 break;
         }
-        if (var.matches("\\d.*")) {
+        if (STARTS_WITH_DIGIT.matcher(var).matches()) {
             var = "_" + var;
         }
         return this.toVarName(var);
@@ -2357,7 +2360,7 @@ private static CodegenModel reconcileInlineEnums(CodegenModel codegenModel, Code
 
     private static String sanitizePackageName(String packageName) {
         packageName = packageName.trim(); // FIXME: a parameter should not be assigned. Also declare the methods parameters as 'final'.
-        packageName = packageName.replaceAll("[^a-zA-Z0-9_\\.]", "_");
+        packageName = INVALID_PACKAGE_CHARS.matcher(packageName).replaceAll("_");
         if (Strings.isNullOrEmpty(packageName)) {
             return "invalidPackageName";
         }
@@ -2366,7 +2369,7 @@ private static String sanitizePackageName(String packageName) {
 
     private String sanitizePath(String p) {
         //prefer replace a ", instead of a fuLL URL encode for readability
-        return p.replaceAll("\"", "%22");
+        return p.replace("\"", "%22");
     }
 
     @Override
@@ -2468,7 +2471,7 @@ public String sanitizeTag(String tag) {
         tag = camelize(underscore(sanitizeName(tag)));
 
         // tag starts with numbers
-        if (tag.matches("^\\d.*")) {
+        if (STARTS_WITH_DIGIT.matcher(tag).matches()) {
             tag = "Class" + tag;
         }
         return tag;
diff --git a/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/AbstractJuliaCodegen.java b/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/AbstractJuliaCodegen.java
index ea5a868b2fa0..c486279217eb 100644
--- a/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/AbstractJuliaCodegen.java
+++ b/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/AbstractJuliaCodegen.java
@@ -40,12 +40,18 @@
 import java.time.OffsetDateTime;
 import java.time.format.DateTimeFormatter;
 import java.util.*;
+import java.util.regex.Pattern;
 
 import static org.openapitools.codegen.utils.StringUtils.camelize;
 
 public abstract class AbstractJuliaCodegen extends DefaultCodegen {
     protected final Logger LOGGER = LoggerFactory.getLogger(AbstractJuliaCodegen.class);
 
+    private static final Pattern SANITIZE_NON_ALPHANUM_BRACE = Pattern.compile("[^a-zA-Z0-9_{}]");
+    private static final Pattern ALNUM_UNDERSCORE = Pattern.compile("[a-zA-Z0-9_]*");
+    private static final Pattern VAR_QUOTED = Pattern.compile("var\".*\"");
+    private static final Pattern DOUBLE_BACKSLASH = Pattern.compile("\\\\\\\\");
+
     protected String srcPath = "src";
     protected String apiSrcPath = srcPath + "/apis/";
     protected String modelSrcPath = srcPath + "/models/";
@@ -157,7 +163,7 @@ public GeneratorLanguage generatorLanguage() {
     }
 
     protected static String dropDots(String str) {
-        return str.replaceAll("\\.", "_");
+        return str.replace(".", "_");
     }
 
     /**
@@ -213,7 +219,7 @@ public String toModelDocFilename(String name) {
 
     @Override
     public String toApiFilename(String name) {
-        name = name.replaceAll("-", "_");
+        name = name.replace("-", "_");
         return "api_" + camelize(name) + "Api";
     }
 
@@ -278,20 +284,20 @@ public String sanitizeName(String name) {
             return "value";
         }
 
-        name = name.replaceAll("\\[\\]", "");
-        name = name.replaceAll("\\[", "_");
-        name = name.replaceAll("\\]", "");
-        name = name.replaceAll("\\(", "_");
-        name = name.replaceAll("\\)", "");
-        name = name.replaceAll("\\.", "_");
-        name = name.replaceAll("-", "_");
-        name = name.replaceAll(" ", "_");
-        name = name.replaceAll("/", "_");
-        return name.replaceAll("[^a-zA-Z0-9_{}]", "");
+        name = name.replace("[]", "");
+        name = name.replace("[", "_");
+        name = name.replace("]", "");
+        name = name.replace("(", "_");
+        name = name.replace(")", "");
+        name = name.replace(".", "_");
+        name = name.replace("-", "_");
+        name = name.replace(" ", "_");
+        name = name.replace("/", "_");
+        return SANITIZE_NON_ALPHANUM_BRACE.matcher(name).replaceAll("");
     }
 
     protected boolean needsVarEscape(String name) {
-        return (!name.matches("[a-zA-Z0-9_]*") && !name.matches("var\".*\"")) || reservedWords.contains(name);
+        return (!ALNUM_UNDERSCORE.matcher(name).matches() && !VAR_QUOTED.matcher(name).matches()) || reservedWords.contains(name);
     }
 
     /**
@@ -310,7 +316,7 @@ public String toModelName(final String name) {
         String result = sanitizeName(name);
 
         // remove dollar sign
-        result = result.replaceAll("$", "");
+        result = result.replace("$", "");
 
         // model name cannot use reserved keyword, e.g. return
         if (isReservedWord(result)) {
@@ -319,7 +325,7 @@ public String toModelName(final String name) {
         }
 
         // model name starts with number
-        if (result.matches("^\\d.*")) {
+        if (STARTS_WITH_DIGIT.matcher(result).matches()) {
             LOGGER.warn(result + " (model name starts with number) cannot be used as model name. Renamed to " + camelize("model_" + result));
             result = "model_" + result; // e.g. 200Response => Model200Response (after camelize)
         }
@@ -514,7 +520,7 @@ public String toRegularExpression(String pattern) {
         pattern = escapeText(pattern);
         // escapeText unnecessarily escapes `\` such that `\.` in the regex ends up as `\\.` for example.
         // we need to restore it back by converting `\\` to `\`
-        pattern = pattern.replaceAll("\\\\\\\\", "\\\\");
+        pattern = DOUBLE_BACKSLASH.matcher(pattern).replaceAll("\\\\");
         return pattern;
     }
 
diff --git a/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/AbstractKotlinCodegen.java b/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/AbstractKotlinCodegen.java
index 545278224b99..014ddf6eb1ac 100644
--- a/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/AbstractKotlinCodegen.java
+++ b/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/AbstractKotlinCodegen.java
@@ -50,6 +50,11 @@
 
 public abstract class AbstractKotlinCodegen extends DefaultCodegen implements CodegenConfig {
 
+    private static final Pattern NON_WORD_UNICODE          = Pattern.compile("\\W+", Pattern.UNICODE_CHARACTER_CLASS);
+    private static final Pattern ALL_UNDERSCORES            = Pattern.compile("^_*$");
+    private static final Pattern LEADING_DIGIT_OR_DOLLAR    = Pattern.compile("(^\\d.*)|(.*\\$.*)");
+    private static final Pattern UNDERSCORE_CLASS           = Pattern.compile("^_*class$");
+
     public static final String MODEL_MUTABLE = "modelMutable";
     public static final String MODEL_MUTABLE_DESC = "Create mutable models";
     public static final String ADDITIONAL_MODEL_TYPE_ANNOTATIONS = "additionalModelTypeAnnotations";
@@ -622,7 +627,7 @@ public String toEnumVarName(String value, String datatype) {
         if (value.isEmpty()) {
             modified = "EMPTY";
         } else {
-            modified = value.replaceAll("-", "_");
+            modified = value.replace("-", "_");
             modified = sanitizeKotlinSpecificNames(modified);
         }
 
@@ -721,7 +726,7 @@ public String toModelName(final String name) {
             return importMapping.get(name);
         }
 
-        String modifiedName = name.replaceAll("\\.", "").replaceAll("-", "_");
+        String modifiedName = name.replace(".", "").replace("-", "_");
 
         String nameWithPrefixSuffix = sanitizeKotlinSpecificNames(modifiedName);
         if (!StringUtils.isEmpty(modelNamePrefix)) {
@@ -745,7 +750,7 @@ public String toModelName(final String name) {
         }
 
         // model name starts with number
-        if (modifiedName.matches("^\\d.*")) {
+        if (STARTS_WITH_DIGIT.matcher(modifiedName).matches()) {
             final String modelName = "Model" + modifiedName; // e.g. 200Response => Model200Response (after camelize)
             LOGGER.warn("{} (model name starts with number) cannot be used as model name. Renamed to {}", name,
                     modelName);
@@ -778,7 +783,7 @@ public String toOperationId(String operationId) {
         }
 
         // operationId starts with a number
-        if (operationId.matches("^\\d.*")) {
+        if (STARTS_WITH_DIGIT.matcher(operationId).matches()) {
             LOGGER.warn(operationId + " (starting with a number) cannot be used as method name. Renamed to " + camelize("call_" + operationId), LOWERCASE_FIRST_LETTER);
             operationId = camelize("call_" + operationId, LOWERCASE_FIRST_LETTER);
         }
@@ -805,14 +810,14 @@ private String sanitizeKotlinSpecificNames(final String name) {
         }
 
         // Fallback, replace unknowns with underscore.
-        word = Pattern.compile("\\W+", Pattern.UNICODE_CHARACTER_CLASS).matcher(word).replaceAll("_");
-        if (word.matches("\\d.*")) {
+        word = NON_WORD_UNICODE.matcher(word).replaceAll("_");
+        if (STARTS_WITH_DIGIT.matcher(word).matches()) {
             word = "_" + word;
         }
 
         // _, __, and ___ are reserved in Kotlin. Treat all names with only underscores consistently, regardless of count.
-        if (word.matches("^_*$")) {
-            word = word.replaceAll("\\Q_\\E", "Underscore");
+        if (ALL_UNDERSCORES.matcher(word).matches()) {
+            word = word.replace("_", "Underscore");
         }
 
         return word;
@@ -1019,7 +1024,7 @@ protected String toVariableName(String name) {
         name = sanitizeName(name, "\\W-[\\$]");
         name = sanitizeKotlinSpecificNames(name);
 
-        if (name.toLowerCase(Locale.ROOT).matches("^_*class$")) {
+        if (UNDERSCORE_CLASS.matcher(name.toLowerCase(Locale.ROOT)).matches()) {
             return "propertyClass";
         }
 
@@ -1028,7 +1033,7 @@ protected String toVariableName(String name) {
         }
 
         // if it's all upper case, do nothing
-        if (name.matches("^[A-Z0-9_]*$")) {
+        if (ALL_UPPER_UNDERSCORE_DIGITS.matcher(name).matches()) {
             return name;
         }
 
@@ -1049,7 +1054,7 @@ protected String toVariableName(String name) {
         name = camelize(name, LOWERCASE_FIRST_LETTER);
 
         // for reserved word or word starting with number or containing dollar symbol, escape it
-        if (isReservedWord(name) || name.matches("(^\\d.*)|(.*[$].*)")) {
+        if (isReservedWord(name) || LEADING_DIGIT_OR_DOLLAR.matcher(name).matches()) {
             name = escapeReservedWord(name);
         }
 
diff --git a/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/AbstractPhpCodegen.java b/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/AbstractPhpCodegen.java
index 68520b123d99..41095056de8e 100644
--- a/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/AbstractPhpCodegen.java
+++ b/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/AbstractPhpCodegen.java
@@ -46,6 +46,13 @@ public abstract class AbstractPhpCodegen extends DefaultCodegen implements Codeg
 
     private final Logger LOGGER = LoggerFactory.getLogger(AbstractPhpCodegen.class);
 
+    private static final Pattern TRAILING_SLASH_BACKSLASH = Pattern.compile("[\\\\/]?$");
+    private static final Pattern PATH_SEPARATOR_CHARS = Pattern.compile("[\\.\\\\/]");
+    private static final Pattern LEADING_AT = Pattern.compile("^@");
+    private static final Pattern NON_WORD_BACKSLASH = Pattern.compile("[^\\w\\\\]+");
+    private static final Pattern STARTS_WITH_BACKSLASH = Pattern.compile("^\\\\.*");
+    private static final Pattern COMPOSER_PACKAGE_NAME = Pattern.compile("^[a-z0-9]([_.-]?[a-z0-9]+)*/[a-z0-9](([_.]?|-{0,2})[a-z0-9]+)*$");
+
     public static final String VARIABLE_NAMING_CONVENTION = "variableNamingConvention";
     public static final String PACKAGE_NAME = "packageName";
     public static final String SRC_BASE_PATH = "srcBasePath";
@@ -295,13 +302,13 @@ public String toSrcPath(final String packageName, final String basePath) {
         String modifiedPackageName = packageName.replace(invokerPackage, "");
         String modifiedBasePath = basePath;
         if (basePath != null && !basePath.isEmpty()) {
-            modifiedBasePath = basePath.replaceAll("[\\\\/]?$", "") + File.separator;
+            modifiedBasePath = TRAILING_SLASH_BACKSLASH.matcher(basePath).replaceAll("") + File.separator;
         }
 
         // Trim prefix file separators from package path
         String packagePath = StringUtils.removeStart(
                 // Replace period, backslash, forward slash with file separator in package name
-                modifiedPackageName.replaceAll("[\\.\\\\/]", Matcher.quoteReplacement("/")),
+                PATH_SEPARATOR_CHARS.matcher(modifiedPackageName).replaceAll(Matcher.quoteReplacement("/")),
                 File.separator
         );
 
@@ -444,7 +451,7 @@ public String toVarName(String name) {
 
         // translate @ for properties (like @type) to at_.
         // Otherwise an additional "type" property will lead to duplicates
-        name = name.replaceAll("^@", "at_");
+        name = LEADING_AT.matcher(name).replaceAll("at_");
 
         // sanitize name
         name = sanitizeName(name); // FIXME: a parameter should not be assigned. Also declare the methods parameters as 'final'.
@@ -465,7 +472,7 @@ public String toVarName(String name) {
 
         // parameter name starting with number won't compile
         // need to escape it by appending _ at the beginning
-        if (name.matches("^\\d.*")) {
+        if (STARTS_WITH_DIGIT.matcher(name).matches()) {
             name = "_" + name;
         }
 
@@ -485,10 +492,10 @@ public String toParamName(String name) {
 
     private String toGenericName(String name) {
         // remove [
-        name = name.replaceAll("\\]", "");
+        name = name.replace("]", "");
 
         // Note: backslash ("\\") is allowed for e.g. "\\DateTime"
-        name = name.replaceAll("[^\\w\\\\]+", "_"); // FIXME: a parameter should not be assigned. Also declare the methods parameters as 'final'.
+        name = NON_WORD_BACKSLASH.matcher(name).replaceAll("_"); // FIXME: a parameter should not be assigned. Also declare the methods parameters as 'final'.
 
         // remove dollar sign
         name = name.replace("$", "");
@@ -500,7 +507,7 @@ private String toGenericName(String name) {
         }
 
         // model name starts with number
-        if (name.matches("^\\d.*")) {
+        if (STARTS_WITH_DIGIT.matcher(name).matches()) {
             LOGGER.warn("{} (model name starts with number) cannot be used as model name. Renamed to {}", name,
                     camelize("model_" + name));
             name = "model_" + name; // e.g. 200Response => Model200Response (after camelize)
@@ -525,7 +532,7 @@ public String toModelName(String name) {
         name = toGenericName(name);
 
         // add prefix and/or suffix only if name does not start with \ (e.g. \DateTime)
-        if (!name.matches("^\\\\.*")) {
+        if (!STARTS_WITH_BACKSLASH.matcher(name).matches()) {
             if (!StringUtils.isEmpty(modelNamePrefix)) {
                 name = modelNamePrefix + "_" + name;
             }
@@ -598,7 +605,7 @@ public String toOperationId(String operationId) {
         }
 
         // operationId starts with a number
-        if (operationId.matches("^\\d.*")) {
+        if (STARTS_WITH_DIGIT.matcher(operationId).matches()) {
             LOGGER.warn("{} (starting with a number) cannot be used as method name. Renamed to {}", operationId, camelize(sanitizeName("call_" + operationId), LOWERCASE_FIRST_LETTER));
             operationId = "call_" + operationId;
         }
@@ -764,20 +771,20 @@ public String toEnumVarName(String name, String datatype) {
 
         // number
         if ("int".equals(datatype) || "float".equals(datatype)) {
-            if (name.matches("\\d.*")) { // starts with number
+            if (STARTS_WITH_DIGIT.matcher(name).matches()) { // starts with number
                 name = "NUMBER_" + name;
             }
-            name = name.replaceAll("-", "MINUS_");
-            name = name.replaceAll("\\+", "PLUS_");
-            name = name.replaceAll("\\.", "_DOT_");
+            name = name.replace("-", "MINUS_");
+            name = name.replace("+", "PLUS_");
+            name = name.replace(".", "_DOT_");
         }
 
         // string
         String enumName = sanitizeName(underscore(name).toUpperCase(Locale.ROOT));
-        enumName = enumName.replaceFirst("^_", "");
-        enumName = enumName.replaceFirst("_$", "");
+        enumName = FIRST_LEADING_UNDERSCORE.matcher(enumName).replaceFirst("");
+        enumName = LAST_TRAILING_UNDERSCORE.matcher(enumName).replaceFirst("");
 
-        if (isReservedWord(enumName) || enumName.matches("\\d.*")) { // reserved word or starts with number
+        if (isReservedWord(enumName) || STARTS_WITH_DIGIT.matcher(enumName).matches()) { // reserved word or starts with number
             return escapeReservedWord(enumName);
         } else {
             return enumName;
@@ -795,7 +802,7 @@ public String toEnumName(CodegenProperty property) {
         // remove [] for array or map of enum
         enumName = enumName.replace("[]", "");
 
-        if (enumName.matches("\\d.*")) { // starts with number
+        if (STARTS_WITH_DIGIT.matcher(enumName).matches()) { // starts with number
             return "_" + enumName;
         } else {
             return enumName;
@@ -907,7 +914,7 @@ public String getComposerPackageName() {
         if (
                 packageName.contentEquals("/")
                         || packageName.contentEquals("null/null")
-                        || !Pattern.matches("^[a-z0-9]([_.-]?[a-z0-9]+)*/[a-z0-9](([_.]?|-{0,2})[a-z0-9]+)*$", packageName)
+                        || !COMPOSER_PACKAGE_NAME.matcher(packageName).matches()
         ) {
             return "";
         }
diff --git a/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/AbstractPythonCodegen.java b/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/AbstractPythonCodegen.java
index a4c775057c47..09a6cdf64e87 100644
--- a/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/AbstractPythonCodegen.java
+++ b/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/AbstractPythonCodegen.java
@@ -49,6 +49,8 @@
 public abstract class AbstractPythonCodegen extends DefaultCodegen implements CodegenConfig {
     private final Logger LOGGER = LoggerFactory.getLogger(AbstractPythonCodegen.class);
 
+    private static final Pattern REGEX_VALUE_EXTRACTOR = Pattern.compile("^/\\^?(.+?)\\$?/.?$");
+
     public static final String MAP_NUMBER_TO = "mapNumberTo";
 
     protected String packageName = "openapi_client";
@@ -220,7 +222,7 @@ public String toDefaultValue(Schema p) {
                 if (defaultValue != null) {
                     defaultValue = defaultValue.replace("\\", "\\\\")
                             .replace("'", "\\'");
-                    if (Pattern.compile("\r\n|\r|\n").matcher(defaultValue).find()) {
+                    if (MULTILINE_STRING.matcher(defaultValue).find()) {
                         return "'''" + defaultValue + "'''";
                     } else {
                         return "'" + defaultValue + "'";
@@ -252,7 +254,7 @@ public String toVarName(String name) {
         name = name.replace("$", "");
 
         // if it's all upper case, convert to lower case
-        if (name.matches("^[A-Z_]*$")) {
+        if (ALL_UPPER_UNDERSCORE.matcher(name).matches()) {
             name = name.toLowerCase(Locale.ROOT);
         }
 
@@ -261,10 +263,10 @@ public String toVarName(String name) {
         name = underscore(name);
 
         // remove leading underscore
-        name = name.replaceAll("^_*", "");
+        name = LEADING_UNDERSCORES.matcher(name).replaceAll("");
 
         // for reserved word or word starting with number, append _
-        if (isReservedWord(name) || name.matches("^\\d.*")) {
+        if (isReservedWord(name) || STARTS_WITH_DIGIT.matcher(name).matches()) {
             name = escapeReservedWord(name);
         }
 
@@ -306,7 +308,7 @@ public String toOperationId(String operationId) {
         }
 
         // operationId starts with a number
-        if (operationId.matches("^\\d.*")) {
+        if (STARTS_WITH_DIGIT.matcher(operationId).matches()) {
             LOGGER.warn("{} (starting with a number) cannot be used as method name. Renamed to {}", operationId, underscore(sanitizeName("call_" + operationId)));
             operationId = "call_" + operationId;
         }
@@ -438,8 +440,7 @@ private String toExampleValueRecursive(Schema schema, List<Schema> includedSchem
                 Random random = new Random(18);
                 String sample = rgxGen.generate(random);
                 // omit leading / and trailing /, omit trailing /i
-                Pattern valueExtractor = Pattern.compile("^/\\^?(.+?)\\$?/.?$");
-                Matcher m = valueExtractor.matcher(sample);
+                Matcher m = REGEX_VALUE_EXTRACTOR.matcher(sample);
                 if (m.find()) {
                     example = m.group(m.groupCount());
                 } else {
@@ -750,7 +751,7 @@ public String toModelName(String name) {
         // remove dollar sign
         sanitizedName = sanitizedName.replace("$", "");
         // remove whitespace
-        sanitizedName = sanitizedName.replaceAll("\\s+", "");
+        sanitizedName = WHITESPACE.matcher(sanitizedName).replaceAll("");
 
         String nameWithPrefixSuffix = sanitizedName;
         if (!StringUtils.isEmpty(modelNamePrefix)) {
@@ -776,7 +777,7 @@ public String toModelName(String name) {
         }
 
         // model name starts with number
-        if (camelizedName.matches("^\\d.*")) {
+        if (STARTS_WITH_DIGIT.matcher(camelizedName).matches()) {
             String modelName = "Model" + camelizedName; // e.g. return => ModelReturn (after camelize)
             LOGGER.warn("{} (model name starts with number) cannot be used as model name. Renamed to {}", camelizedName, modelName);
             schemaKeyToModelNameCache.put(origName, modelName);
@@ -821,7 +822,7 @@ public String toApiVarName(String name) {
     }
 
     protected static String dropDots(String str) {
-        return str.replaceAll("\\.", "_");
+        return str.replace(".", "_");
     }
 
     @Override
@@ -1109,10 +1110,10 @@ public String toEnumVariableName(String name, String datatype) {
         }
 
         name = name.replace(" ", "_");
-        name = name.replaceFirst("^_", "");
-        name = name.replaceFirst("_$", "");
+        name = FIRST_LEADING_UNDERSCORE.matcher(name).replaceFirst("");
+        name = LAST_TRAILING_UNDERSCORE.matcher(name).replaceFirst("");
 
-        if (name.matches("\\d.*")) {
+        if (STARTS_WITH_DIGIT.matcher(name).matches()) {
             name = "ENUM_" + name.toUpperCase(Locale.ROOT);
         }
 
@@ -1381,9 +1382,9 @@ public String addRegularExpressionDelimiter(String pattern) {
             return pattern;
         }
 
-        if (!pattern.matches("^/.*")) {
+        if (!STARTS_WITH_SLASH.matcher(pattern).matches()) {
             // Perform a negative lookbehind on each `/` to ensure that it is escaped.
-            return "/" + pattern.replaceAll("(?<!\\\\)\\/", "\\\\/") + "/";
+            return "/" + UNESCAPED_SLASH.matcher(pattern).replaceAll("\\\\/") + "/";
         }
 
         return pattern;
@@ -1400,7 +1401,7 @@ public String toEnumVarName(String name, String datatype) {
         if ("int".equals(datatype) || "float".equals(datatype)) {
             return name;
         } else {
-            return "\'" + name + "\'";
+            return "'" + name + "'";
         }
     }
 
diff --git a/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/AbstractPythonConnexionServerCodegen.java b/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/AbstractPythonConnexionServerCodegen.java
index a8eec2f60d0a..7ced77d8ffb0 100644
--- a/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/AbstractPythonConnexionServerCodegen.java
+++ b/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/AbstractPythonConnexionServerCodegen.java
@@ -46,6 +46,7 @@
 import java.io.File;
 import java.io.IOException;
 import java.util.*;
+import java.util.regex.Pattern;
 
 import static org.openapitools.codegen.CodegenConstants.X_MODIFIERS;
 import static org.openapitools.codegen.CodegenConstants.X_REGEX;
@@ -71,6 +72,8 @@ public void serialize(Boolean value, JsonGenerator gen, SerializerProvider seria
     public static final String MOVE_TESTS_UNDER_PYTHON_SRC_ROOT = "testsUsePythonSrcRoot";
     static final String MEDIA_TYPE = "mediaType";
 
+    Pattern TRAILING_SLASHES_PATTERN = Pattern.compile("[/\\\\]+$");
+
     // An object mapper that is used to convert an example string to
     // a "python-compliant" example string (boolean as True/False).
     final ObjectMapper MAPPER = new ObjectMapper();
@@ -251,7 +254,7 @@ public void setPythonSrcRoot(String val) {
         if (val == null) {
             pySrcRoot = "";
         } else {
-            pySrcRoot = val.replaceAll("[/\\\\]+$", "");
+            pySrcRoot = TRAILING_SLASHES_PATTERN.matcher(val).replaceAll("");
         }
 
         if (pySrcRoot.isEmpty() || ".".equals(pySrcRoot)) {
diff --git a/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/AbstractPythonPydanticV1Codegen.java b/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/AbstractPythonPydanticV1Codegen.java
index 7591c1df7c37..4c1931c5fcfe 100644
--- a/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/AbstractPythonPydanticV1Codegen.java
+++ b/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/AbstractPythonPydanticV1Codegen.java
@@ -46,11 +46,15 @@
 public abstract class AbstractPythonPydanticV1Codegen extends DefaultCodegen implements CodegenConfig {
     private final Logger LOGGER = LoggerFactory.getLogger(AbstractPythonPydanticV1Codegen.class);
 
+    private static final Pattern REGEX_VALUE_EXTRACTOR = Pattern.compile("^/\\^?(.+?)\\$?/.?$");
+
     public static final String MAP_NUMBER_TO = "mapNumberTo";
 
     protected String packageName = "openapi_client";
-    @Setter protected String packageVersion = "1.0.0";
-    @Setter protected String projectName; // for setup.py, e.g. petstore-api
+    @Setter
+    protected String packageVersion = "1.0.0";
+    @Setter
+    protected String projectName; // for setup.py, e.g. petstore-api
     protected boolean hasModelsToImport = Boolean.FALSE;
     protected String mapNumberTo = "Union[StrictFloat, StrictInt]";
     protected Map<Character, String> regexModifiers;
@@ -190,7 +194,7 @@ public String toDefaultValue(Schema p) {
                 if (defaultValue != null) {
                     defaultValue = defaultValue.replace("\\", "\\\\")
                             .replace("'", "\'");
-                    if (Pattern.compile("\r\n|\r|\n").matcher(defaultValue).find()) {
+                    if (MULTILINE_STRING.matcher(defaultValue).find()) {
                         return "'''" + defaultValue + "'''";
                     } else {
                         return "'" + defaultValue + "'";
@@ -223,7 +227,7 @@ public String toVarName(String name) {
         name = name.replace("$", "");
 
         // if it's all upper case, convert to lower case
-        if (name.matches("^[A-Z_]*$")) {
+        if (ALL_UPPER_UNDERSCORE.matcher(name).matches()) {
             name = name.toLowerCase(Locale.ROOT);
         }
 
@@ -232,10 +236,10 @@ public String toVarName(String name) {
         name = underscore(name);
 
         // remove leading underscore
-        name = name.replaceAll("^_*", "");
+        name = LEADING_UNDERSCORES.matcher(name).replaceAll("");
 
         // for reserved word or word starting with number, append _
-        if (isReservedWord(name) || name.matches("^\\d.*")) {
+        if (isReservedWord(name) || STARTS_WITH_DIGIT.matcher(name).matches()) {
             name = escapeReservedWord(name);
         }
 
@@ -277,7 +281,7 @@ public String toOperationId(String operationId) {
         }
 
         // operationId starts with a number
-        if (operationId.matches("^\\d.*")) {
+        if (STARTS_WITH_DIGIT.matcher(operationId).matches()) {
             LOGGER.warn("{} (starting with a number) cannot be used as method name. Renamed to {}", operationId, underscore(sanitizeName("call_" + operationId)));
             operationId = "call_" + operationId;
         }
@@ -409,8 +413,7 @@ private String toExampleValueRecursive(Schema schema, List<Schema> includedSchem
                 Random random = new Random(18);
                 String sample = rgxGen.generate(random);
                 // omit leading / and trailing /, omit trailing /i
-                Pattern valueExtractor = Pattern.compile("^/\\^?(.+?)\\$?/.?$");
-                Matcher m = valueExtractor.matcher(sample);
+                Matcher m = REGEX_VALUE_EXTRACTOR.matcher(sample);
                 if (m.find()) {
                     example = m.group(m.groupCount());
                 } else {
@@ -702,7 +705,7 @@ public String toModelName(String name) {
         // remove dollar sign
         sanitizedName = sanitizedName.replace("$", "");
         // remove whitespace
-        sanitizedName = sanitizedName.replaceAll("\\s+", "");
+        sanitizedName = WHITESPACE.matcher(sanitizedName).replaceAll("");
 
         String nameWithPrefixSuffix = sanitizedName;
         if (!StringUtils.isEmpty(modelNamePrefix)) {
@@ -728,7 +731,7 @@ public String toModelName(String name) {
         }
 
         // model name starts with number
-        if (camelizedName.matches("^\\d.*")) {
+        if (STARTS_WITH_DIGIT.matcher(camelizedName).matches()) {
             String modelName = "Model" + camelizedName; // e.g. return => ModelReturn (after camelize)
             LOGGER.warn("{} (model name starts with number) cannot be used as model name. Renamed to {}", camelizedName, modelName);
             schemaKeyToModelNameCache.put(origName, modelName);
@@ -773,7 +776,7 @@ public String toApiVarName(String name) {
     }
 
     protected static String dropDots(String str) {
-        return str.replaceAll("\\.", "_");
+        return  DOT.matcher(str).replaceAll("_");
     }
 
     @Override
@@ -1625,10 +1628,10 @@ public String toEnumVariableName(String name, String datatype) {
         }
 
         name = name.replace(" ", "_");
-        name = name.replaceFirst("^_", "");
-        name = name.replaceFirst("_$", "");
+        name = FIRST_LEADING_UNDERSCORE.matcher(name).replaceFirst("");
+        name = LAST_TRAILING_UNDERSCORE.matcher(name).replaceFirst("");
 
-        if (name.matches("\\d.*")) {
+        if (STARTS_WITH_DIGIT.matcher(name).matches()) {
             name = "ENUM_" + name.toUpperCase(Locale.ROOT);
         }
 
@@ -1929,9 +1932,9 @@ public String addRegularExpressionDelimiter(String pattern) {
             return pattern;
         }
 
-        if (!pattern.matches("^/.*")) {
+        if (!STARTS_WITH_SLASH.matcher(pattern).matches()) {
             // Perform a negative lookbehind on each `/` to ensure that it is escaped.
-            return "/" + pattern.replaceAll("(?<!\\\\)\\/", "\\\\/") + "/";
+            return "/" + UNESCAPED_SLASH.matcher(pattern).replaceAll("\\\\/") + "/";
         }
 
         return pattern;
diff --git a/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/AbstractRubyCodegen.java b/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/AbstractRubyCodegen.java
index 0c406486822f..62920a326d52 100644
--- a/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/AbstractRubyCodegen.java
+++ b/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/AbstractRubyCodegen.java
@@ -180,7 +180,7 @@ public String toVarName(final String name) {
 
         String varName = sanitizeName(name);
         // if it's all upper case, convert to lower case
-        if (name.matches("^[A-Z_]*$")) {
+        if (ALL_UPPER_UNDERSCORE.matcher(name).matches()) {
             varName = varName.toLowerCase(Locale.ROOT);
         }
 
@@ -189,7 +189,7 @@ public String toVarName(final String name) {
         varName = underscore(varName);
 
         // for reserved word or word starting with number, append _
-        if (isReservedWord(varName) || varName.matches("^\\d.*")) {
+        if (isReservedWord(varName) || STARTS_WITH_DIGIT.matcher(varName).matches()) {
             varName = escapeReservedWord(varName);
         }
 
@@ -207,9 +207,9 @@ public String addRegularExpressionDelimiter(String pattern) {
             return pattern;
         }
 
-        if (!pattern.matches("^/.*")) {
+        if (!STARTS_WITH_SLASH.matcher(pattern).matches()) {
             // Perform a negative lookbehind on each `/` to ensure that it is escaped.
-            return "/" + pattern.replaceAll("(?<!\\\\)\\/", "\\\\/") + "/";
+            return "/" + UNESCAPED_SLASH.matcher(pattern).replaceAll("\\\\/") + "/";
         }
 
         return pattern;
diff --git a/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/AbstractRustCodegen.java b/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/AbstractRustCodegen.java
index 39e888bae0f7..5b8b4300ff82 100644
--- a/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/AbstractRustCodegen.java
+++ b/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/AbstractRustCodegen.java
@@ -14,6 +14,7 @@
 import java.math.BigInteger;
 import java.util.*;
 import java.util.function.Function;
+import java.util.regex.Pattern;
 
 import static org.openapitools.codegen.utils.StringUtils.*;
 
@@ -21,6 +22,9 @@ public abstract class AbstractRustCodegen extends DefaultCodegen implements Code
 
     private final Logger LOGGER = LoggerFactory.getLogger(AbstractRustCodegen.class);
 
+    /** Matches hyphens and periods — replaced with underscores during name sanitisation. */
+    private static final Pattern HYPHEN_OR_PERIOD = Pattern.compile("[.\\-]");
+
     protected static final String VENDOR_EXTENSION_PARAM_IDENTIFIER = "x-rust-param-identifier";
 
     protected List<String> charactersToAllow = Collections.singletonList("_");
@@ -184,7 +188,7 @@ public String sanitizeIdentifier(String name, CasingType casingType, String esca
         }
 
         // Replace hyphens and periods with underscores
-        name = name.replaceAll("[\\.\\-]", "_");
+        name = HYPHEN_OR_PERIOD.matcher(name).replaceAll("_");
 
         // Apply special character escapes, e.g. "@type" => "At_type"
         // Remove the trailing underscore if necessary
@@ -207,7 +211,7 @@ public String sanitizeIdentifier(String name, CasingType casingType, String esca
 
         // If word starts with number add a prefix
         // Note: this must be done after casing since CamelCase will strip leading underscores
-        if (name.matches("^\\d.*")) {
+        if (STARTS_WITH_DIGIT.matcher(name).matches()) {
             nameWasModified = true;
             name = casingFunction.apply(escapePrefix + '_' + name);
         }
diff --git a/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/AbstractScalaCodegen.java b/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/AbstractScalaCodegen.java
index d453d882e57b..f93800dc53a2 100644
--- a/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/AbstractScalaCodegen.java
+++ b/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/AbstractScalaCodegen.java
@@ -37,6 +37,7 @@
 import java.io.StringWriter;
 import java.io.Writer;
 import java.util.*;
+import java.util.regex.Pattern;
 
 import static org.openapitools.codegen.languages.AbstractJavaCodegen.DATE_LIBRARY;
 import static org.openapitools.codegen.utils.CamelizeOption.LOWERCASE_FIRST_LETTER;
@@ -47,6 +48,11 @@
 public abstract class AbstractScalaCodegen extends DefaultCodegen {
     private final Logger LOGGER = LoggerFactory.getLogger(AbstractScalaCodegen.class);
 
+    /** Matches a valid Java/Scala identifier starting with a letter, {@code _} or {@code $}. */
+    private static final Pattern SCALA_IDENTIFIER = Pattern.compile("[a-zA-Z_$][\\w_$]+");
+    /** Matches a string consisting only of digits (possibly empty). */
+    private static final Pattern DIGITS_ZERO_OR_MORE = Pattern.compile("[0-9]*");
+
     // https://spec.openapis.org/registry/format/date-time-local.html
     protected static final String DATE_TIME_LOCAL_FORMAT = "date-time-local";
 
@@ -288,11 +294,11 @@ public String toVarName(String name) {
         }
 
         // if it's all upper case, do nothing
-        if (!varName.matches("^[A-Z_0-9]*$")) {
+        if (!ALL_UPPER_UNDERSCORE_DIGITS.matcher(varName).matches()) {
             varName = getNameUsingModelPropertyNaming(varName);
         }
 
-        if (isReservedWord(varName) || varName.matches("^\\d.*")) {
+        if (isReservedWord(varName) || STARTS_WITH_DIGIT.matcher(varName).matches()) {
             varName = escapeReservedWord(varName);
         }
 
@@ -502,7 +508,7 @@ public String toModelName(final String name) {
         }
 
         // model name starts with number
-        if (name.matches("^\\d.*")) {
+        if (STARTS_WITH_DIGIT.matcher(name).matches()) {
             final String modelName = "Model" + camelizedName; // e.g. 200Response => Model200Response (after camelize)
             LOGGER.warn("{} (model name starts with number) cannot be used as model name. Renamed to {}", name,
                     modelName);
@@ -531,13 +537,13 @@ protected String formatIdentifier(String name, boolean capitalized) {
         if (capitalized) {
             identifier = StringUtils.capitalize(identifier);
         }
-        if (identifier.matches("[a-zA-Z_$][\\w_$]+") && !isReservedWord(identifier)) {
+        if (SCALA_IDENTIFIER.matcher(identifier).matches() && !isReservedWord(identifier)) {
             return identifier;
         }
 
         // below code block only for scala-sttp4-jsoniter for backward copmatibility
         if (this instanceof ScalaSttp4JsoniterClientCodegen) {
-            if (identifier.matches("[0-9]*")) {
+            if (DIGITS_ZERO_OR_MORE.matcher(identifier).matches()) {
                 return escapeReservedWord(identifier);
             }
             if (!capitalized || StringUtils.isNumeric(name)) {
@@ -601,7 +607,7 @@ public String toOperationId(String operationId) {
         }
 
         // operationId starts with a number
-        if (operationId.matches("^\\d.*")) {
+        if (STARTS_WITH_DIGIT.matcher(operationId).matches()) {
             LOGGER.warn(operationId + " (starting with a number) cannot be used as method sname. Renamed to " + camelize("call_" + operationId), true);
             operationId = camelize("call_" + operationId, LOWERCASE_FIRST_LETTER);
         }
diff --git a/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/AbstractTypeScriptClientCodegen.java b/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/AbstractTypeScriptClientCodegen.java
index 9f09d9c5cb14..d08229ca2e2e 100644
--- a/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/AbstractTypeScriptClientCodegen.java
+++ b/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/AbstractTypeScriptClientCodegen.java
@@ -79,6 +79,11 @@
 
 public abstract class AbstractTypeScriptClientCodegen extends DefaultCodegen implements CodegenConfig {
 
+    /** Splits a composed TypeScript type string on {@code |}, {@code &}, {@code <}, or {@code >}. */
+    private static final Pattern COMPOSED_TYPE_DELIMITERS = Pattern.compile("[|&<>]");
+    /** Matches NPM versions that end with {@code -SNAPSHOT}. */
+    private static final Pattern SNAPSHOT_VERSION = Pattern.compile("^.*-SNAPSHOT$");
+
     /**
      * Help generating code for any kind of URL parameters (path, matrix, query).
      * <p>
@@ -491,7 +496,7 @@ public Map<String, String> toModelImportMap(String name) {
     }
 
     private String[] splitComposedType(String name) {
-        return name.replace(" ", "").split("[|&<>]");
+        return COMPOSED_TYPE_DELIMITERS.split(name.replace(" ", ""));
     }
 
     private boolean isUnionType(String name) {
@@ -526,7 +531,7 @@ public void preprocessOpenAPI(OpenAPI openAPI) {
             }
 
             if (additionalProperties.containsKey(SNAPSHOT) && Boolean.parseBoolean(additionalProperties.get(SNAPSHOT).toString())) {
-                if (npmVersion.toUpperCase(Locale.ROOT).matches("^.*-SNAPSHOT$")) {
+                if (SNAPSHOT_VERSION.matcher(npmVersion.toUpperCase(Locale.ROOT)).matches()) {
                     this.setNpmVersion(npmVersion + "." + SNAPSHOT_SUFFIX_FORMAT.get().format(new Date()));
                 } else {
                     this.setNpmVersion(npmVersion + "-SNAPSHOT." + SNAPSHOT_SUFFIX_FORMAT.get().format(new Date()));
@@ -601,7 +606,7 @@ public String toVarName(String name) {
     }
 
     private String toSafeIdentifier(String name) {
-        if (isReservedWord(name) || name.matches("^\\d.*")) {
+        if (isReservedWord(name) || STARTS_WITH_DIGIT.matcher(name).matches()) {
             name = escapeReservedWord(name);
         }
         return name;
@@ -650,7 +655,7 @@ protected String toTypescriptTypeName(final String name, String safePrefix) {
         }
 
         // model name starts with number
-        if (sanName.matches("^\\d.*")) {
+        if (STARTS_WITH_DIGIT.matcher(sanName).matches()) {
             String modelName = safePrefix + sanName; // e.g. 200Response => Model200Response
             LOGGER.warn("{} (model name starts with number) cannot be used as model name. Renamed to {}", sanName,
                     modelName);
@@ -961,25 +966,25 @@ public String toEnumVarName(String name, String datatype) {
         if ("number".equals(datatype)) {
             varName = "NUMBER_" + varName;
 
-            varName = varName.replaceAll("-", "MINUS_");
-            varName = varName.replaceAll("\\+", "PLUS_");
-            varName = varName.replaceAll("\\.", "_DOT_");
+            varName = MINUS.matcher(varName).replaceAll("MINUS_");
+            varName = PLUS.matcher(varName).replaceAll("PLUS_");
+            varName = DOT.matcher(varName).replaceAll("_DOT_");
             return varName;
         }
 
         // string
         if (isEnumPropertyNamingReplaceSpecialChar()) {
-            varName = varName.replaceAll("-", "_minus_");
-            varName = varName.replaceAll("\\+", "_plus_");
-            varName = varName.replaceAll("_+", "_");
+            varName = MINUS.matcher(varName).replaceAll("_minus_");
+            varName = PLUS.matcher(varName).replaceAll("_plus_");
+            varName = MULTI_UNDERSCORES.matcher(varName).replaceAll("_");
         }
         varName = sanitizeName(varName);
-        varName = varName.replaceFirst("^_", "");
-        varName = varName.replaceFirst("_$", "");
+        varName = FIRST_LEADING_UNDERSCORE.matcher(varName).replaceFirst("");
+        varName = LAST_TRAILING_UNDERSCORE.matcher(varName).replaceFirst("");
 
         varName = getNameUsingEnumPropertyNaming(varName);
 
-        if (varName.matches("\\d.*")) { // starts with number
+        if (STARTS_WITH_DIGIT.matcher(varName).matches()) { // starts with number
             return "_" + varName;
         } else {
             return varName;
@@ -1207,7 +1212,7 @@ public String escapeText(String input) {
         }
 
         // replace ' with \'
-        return super.escapeText(input).replace("\'", "\\\'");
+        return super.escapeText(input).replace("'", "\\'");
     }
 
     @Override
diff --git a/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/AdaCodegen.java b/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/AdaCodegen.java
index 45c87f8b1c3b..4ca6694e8355 100644
--- a/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/AdaCodegen.java
+++ b/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/AdaCodegen.java
@@ -103,7 +103,7 @@ public void processOpts() {
         } else {
             // default: set project based on package name
             // e.g. petstore.api (package name) => petstore_api (project name)
-            projectName = packageName.replaceAll("\\.", "_");
+            projectName = DOT.matcher(packageName).replaceAll("_");
         }
         String configBaseName = modelPackage.toLowerCase(Locale.ROOT);
         supportingFiles.add(new SupportingFile("gnat-project.mustache", "", toFilename(projectName) + ".gpr"));
@@ -125,7 +125,7 @@ public void processOpts() {
         additionalProperties.put("httpClientGprName", httpClientPackageName.toLowerCase(Locale.ROOT));
         additionalProperties.put(CodegenConstants.PROJECT_NAME, projectName);
 
-        String[] names = this.modelPackage.split("\\.");
+        String[] names = DOT.split(this.modelPackage);
         String pkgName = names[0];
         additionalProperties.put("packageLevel1", pkgName);
         supportingFiles.add(new SupportingFile("package-spec-level1.mustache", "src",
@@ -146,8 +146,8 @@ public void processOpts() {
             @Override
             public void execute(Template.Fragment fragment, Writer writer) throws IOException {
                 String content = fragment.execute();
-                content = content.trim().replaceAll("\n$", "");
-                writer.write(content.replaceAll("\n", "\n   --  "));
+                content = TRAILING_NEWLINE.matcher(content.trim()).replaceAll("");
+                writer.write(NEWLINE.matcher(content).replaceAll("\n   --  "));
             }
         });
     }
diff --git a/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/AdaServerCodegen.java b/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/AdaServerCodegen.java
index afc3690d21e0..300ebc4254b3 100644
--- a/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/AdaServerCodegen.java
+++ b/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/AdaServerCodegen.java
@@ -108,7 +108,7 @@ public void processOpts() {
         } else {
             // default: set project based on package name
             // e.g. petstore.api (package name) => petstore_api (project name)
-            projectName = packageName.replaceAll("\\.", "_");
+            projectName = DOT.matcher(packageName).replaceAll("_");
         }
         String configBaseName = modelPackage.toLowerCase(Locale.ROOT);
         supportingFiles.add(new SupportingFile("gnat-project.mustache", "", toFilename(projectName) + ".gpr"));
@@ -131,7 +131,7 @@ public void processOpts() {
         additionalProperties.put("httpClientGprName", httpClientPackageName.toLowerCase(Locale.ROOT));
         additionalProperties.put(CodegenConstants.PROJECT_NAME, projectName);
 
-        String names[] = this.modelPackage.split("\\.");
+        String names[] = DOT.split(this.modelPackage);
         String pkgName = names[0];
         additionalProperties.put("packageLevel1", pkgName);
         supportingFiles.add(new SupportingFile("package-spec-level1.mustache", "src",
@@ -152,8 +152,8 @@ public void processOpts() {
             @Override
             public void execute(Template.Fragment fragment, Writer writer) throws IOException {
                 String content = fragment.execute();
-                content = content.trim().replaceAll("\n$", "");
-                writer.write(content.replaceAll("\n", "\n   --  "));
+                content = TRAILING_NEWLINE.matcher(content.trim()).replaceAll("");
+                writer.write(NEWLINE.matcher(content).replaceAll("\n   --  "));
             }
         });
     }
diff --git a/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/AndroidClientCodegen.java b/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/AndroidClientCodegen.java
index b94c939f8e1a..f6a54a0f5071 100644
--- a/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/AndroidClientCodegen.java
+++ b/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/AndroidClientCodegen.java
@@ -260,10 +260,10 @@ public String toVarName(String name) {
         name = sanitizeName(name); // FIXME: a parameter should not be assigned. Also declare the methods parameters as 'final'.
 
         // replace - with _ e.g. created-at => created_at
-        name = name.replaceAll("-", "_"); // FIXME: a parameter should not be assigned. Also declare the methods parameters as 'final'.
+        name = MINUS.matcher(name).replaceAll("_"); // FIXME: a parameter should not be assigned. Also declare the methods parameters as 'final'.
 
         // if it's all upper case, do nothing
-        if (name.matches("^[A-Z_]*$")) {
+        if (ALL_UPPER_UNDERSCORE.matcher(name).matches()) {
             return name;
         }
 
@@ -272,7 +272,7 @@ public String toVarName(String name) {
         name = camelize(name, LOWERCASE_FIRST_LETTER);
 
         // for reserved word or word starting with number, append _
-        if (isReservedWord(name) || name.matches("^\\d.*")) {
+        if (isReservedWord(name) || STARTS_WITH_DIGIT.matcher(name).matches()) {
             name = escapeReservedWord(name);
         }
 
@@ -308,7 +308,7 @@ public String toModelName(String name) {
         }
 
         // model name starts with number
-        if (name.matches("^\\d.*")) {
+        if (STARTS_WITH_DIGIT.matcher(name).matches()) {
             String modelName = "Model" + name; // e.g. 200Response => Model200Response (after camelize)
             LOGGER.warn("{} (model name starts with number) cannot be used as model name. Renamed to {}", name,
                     modelName);
diff --git a/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/AsciidocDocumentationCodegen.java b/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/AsciidocDocumentationCodegen.java
index 42f56a8bcce2..14299508433f 100644
--- a/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/AsciidocDocumentationCodegen.java
+++ b/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/AsciidocDocumentationCodegen.java
@@ -98,7 +98,7 @@ public void execute(final Template.Fragment frag, final Writer out) throws IOExc
         }
 
         private String escapeCurlyBrackets(String relativeFileName) {
-            return relativeFileName.replaceAll("\\{", "\\\\{").replaceAll("\\}", "\\\\}");
+            return RIGHT_CURLY_BRACE.matcher(LEFT_CURLY_BRACE.matcher(relativeFileName).replaceAll("\\\\{")).replaceAll("\\\\}");
         }
     }
 
diff --git a/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/AvroSchemaCodegen.java b/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/AvroSchemaCodegen.java
index 572ec6f64777..5b6dab70737b 100644
--- a/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/AvroSchemaCodegen.java
+++ b/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/AvroSchemaCodegen.java
@@ -252,7 +252,7 @@ protected List<Map<String, Object>> buildEnumVars(List<Object> values, String da
      */
     private String sanitizeEnumValue(String value) {
         // Replace any non-alphanumeric characters with an underscore
-        String sanitizedValue = value.replaceAll("[^A-Za-z0-9_]", "_");
+        String sanitizedValue = NON_WORD_CHAR.matcher(value).replaceAll("_");
         // If the enum starts with a number, prefix it with an underscore
         sanitizedValue = sanitizedValue.replaceAll("^([0-9])", "_$1");
         return sanitizedValue;
diff --git a/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/BashClientCodegen.java b/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/BashClientCodegen.java
index 2fa2b92d03fd..0d0ae19e9299 100644
--- a/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/BashClientCodegen.java
+++ b/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/BashClientCodegen.java
@@ -58,6 +58,18 @@ public class BashClientCodegen extends DefaultCodegen implements CodegenConfig {
 
     protected static int emptyMethodNameCounter = 0;
 
+    // --- Precompiled patterns for markdown-to-bash conversion ---
+    private static final java.util.regex.Pattern MD_BOLD_STAR       = java.util.regex.Pattern.compile("(?m)(^|\\s)\\*{2}([\\w ]+)\\*{2}($|\\s)");
+    private static final java.util.regex.Pattern MD_BOLD_UNDERSCORE = java.util.regex.Pattern.compile("(?m)(^|\\s)_{2}([\\w ]+)_{2}($|\\s)");
+    private static final java.util.regex.Pattern MD_ITALIC_STAR     = java.util.regex.Pattern.compile("(?m)(^|\\s)\\*([\\w ]+)\\*($|\\s)");
+    private static final java.util.regex.Pattern MD_ITALIC_UNDER    = java.util.regex.Pattern.compile("(?m)(^|\\s)_([\\w ]+)_($|\\s)");
+    private static final java.util.regex.Pattern MD_H1              = java.util.regex.Pattern.compile("(?m)^#\\s+(.+)$");
+    private static final java.util.regex.Pattern MD_H2              = java.util.regex.Pattern.compile("(?m)^##\\s+(.+)$");
+    private static final java.util.regex.Pattern MD_H3              = java.util.regex.Pattern.compile("(?m)^###\\s+(.+)$");
+    private static final java.util.regex.Pattern MD_CODE_BACKTICK   = java.util.regex.Pattern.compile("(?m)\\s*```.*$");
+    private static final java.util.regex.Pattern MD_CODE_QUOTE      = java.util.regex.Pattern.compile("(?m)\\s*'''.*$");
+    private static final java.util.regex.Pattern MD_TRAILING_WS     = java.util.regex.Pattern.compile("\\s+$");
+
     public static final String CURL_OPTIONS = "curlOptions";
     public static final String PROCESS_MARKDOWN = "processMarkdown";
     public static final String SCRIPT_NAME = "scriptName";
@@ -510,56 +522,45 @@ public String escapeText(String input) {
              * Convert markdown strong **Bold text**  and __Bold text__
              * to bash bold control sequences (tput bold)
              */
-            result = result.replaceAll("(?m)(^|\\s)\\*{2}([\\w\\d ]+)\\*{2}($|\\s)",
-                    "\\$\\(tput bold\\) $2 \\$\\(tput sgr0\\)");
+            result = MD_BOLD_STAR.matcher(result).replaceAll("\\$\\(tput bold\\) $2 \\$\\(tput sgr0\\)");
+            result = MD_BOLD_UNDERSCORE.matcher(result).replaceAll("\\$\\(tput bold\\) $2 \\$\\(tput sgr0\\)");
 
-            result = result.replaceAll("(?m)(^|\\s)_{2}([\\w\\d ]+)_{2}($|\\s)",
-                    "\\$\\(tput bold\\) $2 \\$\\(tput sgr0\\)");
             /**
              * Convert markdown *Italics text* and _Italics text_ to bash dim
              * control sequences (tput dim)
              */
-            result = result.replaceAll("(?m)(^|\\s)\\*{1}([\\w\\d ]+)\\*{1}($|\\s)",
-                    "\\$\\(tput dim\\) $2 \\$\\(tput sgr0\\)");
-
-            result = result.replaceAll("(?m)(^|\\s)_{1}([\\w\\d ]+)_{1}($|\\s)",
-                    "\\$\\(tput dim\\) $2 \\$\\(tput sgr0\\)");
+            result = MD_ITALIC_STAR.matcher(result).replaceAll("\\$\\(tput dim\\) $2 \\$\\(tput sgr0\\)");
+            result = MD_ITALIC_UNDER.matcher(result).replaceAll("\\$\\(tput dim\\) $2 \\$\\(tput sgr0\\)");
 
 
             /**
              * Convert all markdown section 1 level headers with bold
              */
-            result = result.replaceAll("(?m)^\\#\\s+(.+)$",
-                    "\n\\$\\(tput bold\\)\\$\\(tput setaf 7\\)"
-                            + "$1\\$\\(tput sgr0\\)");
+            result = MD_H1.matcher(result).replaceAll("\n\\$\\(tput bold\\)\\$\\(tput setaf 7\\)"
+                    + "$1\\$\\(tput sgr0\\)");
 
             /**
              * Convert all markdown section 2 level headers with bold
              */
-            result = result.replaceAll("(?m)^\\#\\#\\s+(.+)$",
-                    "\n\\$\\(tput bold\\)\\$\\(tput setaf 7\\)"
-                            + "$1\\$\\(tput sgr0\\)");
+            result = MD_H2.matcher(result).replaceAll("\n\\$\\(tput bold\\)\\$\\(tput setaf 7\\)"
+                    + "$1\\$\\(tput sgr0\\)");
 
             /**
              * Convert all markdown section 3 level headers with bold
              */
-            result = result.replaceAll("(?m)^\\#\\#\\#\\s+(.+)$",
-                    "\n\\$\\(tput bold\\)\\$\\(tput setaf 7\\)"
-                            + "$1\\$\\(tput sgr0\\)");
+            result = MD_H3.matcher(result).replaceAll("\n\\$\\(tput bold\\)\\$\\(tput setaf 7\\)"
+                    + "$1\\$\\(tput sgr0\\)");
 
             /**
              * Convert all markdown code blocks into --- delimited sections
              */
-            result = result.replaceAll("(?m)\\s*```.*$",
-                    "\n---");
-
-            result = result.replaceAll("(?m)\\s*\\'\\'\\'.*$",
-                    "\n---");
+            result = MD_CODE_BACKTICK.matcher(result).replaceAll("\n---");
+            result = MD_CODE_QUOTE.matcher(result).replaceAll("\n---");
 
             /**
              * Remove any trailing new line at the end of the string
              */
-            result = result.replaceAll("\\s+$", "");
+            result = MD_TRAILING_WS.matcher(result).replaceAll("");
         }
 
         return result;
@@ -583,7 +584,7 @@ public String escapeUnsafeCharacters(String input) {
         /**
          * Replace backticks with normal single quotes.
          */
-        String result = input.replaceAll("`", "'");
+        String result = input.replace("`", "'");
 
         return result;
     }
@@ -787,7 +788,7 @@ public String toOperationId(String operationId) {
         }
 
         // operationId starts with a number
-        if (operationId.matches("^\\d.*")) {
+        if (STARTS_WITH_DIGIT.matcher(operationId).matches()) {
             LOGGER.warn("{} (starting with a number) cannot be used as method name. Renamed to {}", operationId, underscore(sanitizeName("call_" + operationId)));
             operationId = "call_" + operationId;
         }
diff --git a/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/CLibcurlClientCodegen.java b/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/CLibcurlClientCodegen.java
index 406c32d0f965..b161f5f69d1e 100644
--- a/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/CLibcurlClientCodegen.java
+++ b/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/CLibcurlClientCodegen.java
@@ -605,14 +605,14 @@ public String toVarName(String name) {
         // sanitize name
         name = sanitizeName(name); // FIXME: a parameter should not be assigned. Also declare the methods parameters as 'final'.
         // if it's all upper case, convert to lower case
-        if (name.matches("^[A-Z_]*$")) {
+        if (ALL_UPPER_UNDERSCORE.matcher(name).matches()) {
             name = name.toLowerCase(Locale.ROOT);
         }
 
         name = underscore(name);
 
         // for reserved word or word starting with number, append _
-        if (isReservedWord(name) || name.matches("^\\d.*")) {
+        if (isReservedWord(name) || STARTS_WITH_DIGIT.matcher(name).matches()) {
             name = escapeReservedWord(name);
         }
 
@@ -627,10 +627,10 @@ public String toParamName(String name) {
         }
 
         // should be the same as variable name
-        if (isReservedWord(name) || name.matches("^\\d.*")) {
+        if (isReservedWord(name) || STARTS_WITH_DIGIT.matcher(name).matches()) {
             name = escapeReservedWord(name);
         }
-        name = name.replaceAll("-", "_");
+        name = MINUS.matcher(name).replaceAll("_");
         return name;
     }
 
@@ -659,7 +659,7 @@ public String toModelName(String name) {
         }
 
         // model name starts with number
-        if (name.matches("^\\d.*")) {
+        if (STARTS_WITH_DIGIT.matcher(name).matches()) {
             LOGGER.warn("{} (model name starts with number) cannot be used as model name. Renamed to {}", name,
                     camelize("model_" + name));
             name = "model_" + name; // e.g. 200Response => Model200Response (after camelize)
@@ -683,7 +683,7 @@ public String toModelDocFilename(String name) {
     @Override
     public String toApiFilename(String name) {
         // replace - with _ e.g. created-at => created_at
-        name = name.replaceAll("-", "_"); // FIXME: a parameter should not be assigned. Also declare the methods parameters as 'final'.
+        name = MINUS.matcher(name).replaceAll("_"); // FIXME: a parameter should not be assigned. Also declare the methods parameters as 'final'.
 
         // e.g. PhoneNumberApi.rb => phone_number_api.rb
         return camelize(name) + "API";
@@ -715,14 +715,14 @@ public String toApiName(String name) {
 
     @Override
     public String toEnumValue(String value, String datatype) {
-        value = value.replaceAll("-", "_");
+        value = MINUS.matcher(value).replaceAll("_");
         if (isReservedWord(value)) {
             value = escapeReservedWord(value);
         }
         if ("Integer".equals(datatype) || "Float".equals(datatype)) {
             return value;
         } else {
-            if (value.matches("\\d.*")) { // starts with number
+            if (STARTS_WITH_DIGIT.matcher(value).matches()) { // starts with number
                 return escapeReservedWord(escapeText(value));
             } else {
                 return escapeText(value);
@@ -739,18 +739,18 @@ public String toEnumVarName(String name, String datatype) {
         // number
         if ("Integer".equals(datatype) || "Float".equals(datatype)) {
             String varName = name;
-            varName = varName.replaceAll("-", "MINUS_");
-            varName = varName.replaceAll("\\+", "PLUS_");
-            varName = varName.replaceAll("\\.", "_DOT_");
+            varName = MINUS.matcher(varName).replaceAll("MINUS_");
+            varName = PLUS.matcher(varName).replaceAll("PLUS_");
+            varName = DOT.matcher(varName).replaceAll("_DOT_");
             return varName;
         }
 
         // string
         String enumName = sanitizeName(camelize(name).toUpperCase(Locale.ROOT));
-        enumName = enumName.replaceFirst("^_", "");
-        enumName = enumName.replaceFirst("_$", "");
+        enumName = FIRST_LEADING_UNDERSCORE.matcher(enumName).replaceFirst("");
+        enumName = LAST_TRAILING_UNDERSCORE.matcher(enumName).replaceFirst("");
 
-        if (enumName.matches("\\d.*")) { // starts with number
+        if (STARTS_WITH_DIGIT.matcher(enumName).matches()) { // starts with number
             return escapeReservedWord(enumName);
         } else {
             return enumName;
@@ -760,10 +760,10 @@ public String toEnumVarName(String name, String datatype) {
     @Override
     public String toEnumName(CodegenProperty property) {
         String enumName = camelize(toModelName(property.name)).toUpperCase(Locale.ROOT);
-        enumName = enumName.replaceFirst("^_", "");
-        enumName = enumName.replaceFirst("_$", "");
+        enumName = FIRST_LEADING_UNDERSCORE.matcher(enumName).replaceFirst("");
+        enumName = LAST_TRAILING_UNDERSCORE.matcher(enumName).replaceFirst("");
 
-        if (enumName.matches("\\d.*")) { // starts with number
+        if (STARTS_WITH_DIGIT.matcher(enumName).matches()) { // starts with number
             return escapeReservedWord(enumName);
         } else {
             return enumName;
@@ -793,7 +793,7 @@ public String toOperationId(String operationId) {
         }
 
         // operationId starts with a number
-        if (operationId.matches("^\\d.*")) {
+        if (STARTS_WITH_DIGIT.matcher(operationId).matches()) {
             String newOperationId = camelize(sanitizeName("call_" + operationId), LOWERCASE_FIRST_LETTER);
             LOGGER.warn("{} (starting with a number) cannot be used as method name. Renamed to {}", operationId, newOperationId);
             return newOperationId;
diff --git a/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/CSharpClientCodegen.java b/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/CSharpClientCodegen.java
index e087bfda2a25..a37e0117d717 100644
--- a/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/CSharpClientCodegen.java
+++ b/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/CSharpClientCodegen.java
@@ -1316,18 +1316,18 @@ public String toEnumVarName(String value, String datatype) {
                 datatype.startsWith("long") || datatype.startsWith("ulong") ||
                 datatype.startsWith("double") || datatype.startsWith("float")) {
             String varName = "NUMBER_" + value;
-            varName = varName.replaceAll("-", "MINUS_");
-            varName = varName.replaceAll("\\+", "PLUS_");
-            varName = varName.replaceAll("\\.", "_DOT_");
+            varName = MINUS.matcher(varName).replaceAll("MINUS_");
+            varName = PLUS.matcher(varName).replaceAll("PLUS_");
+            varName = DOT.matcher(varName).replaceAll("_DOT_");
             return varName;
         }
 
         // string
-        String var = value.replaceAll(" ", "_");
+        String var = value.replace(" ", "_");
         var = camelize(var);
-        var = var.replaceAll("\\W+", "");
+        var = NON_WORD_PLUS.matcher(var).replaceAll("");
 
-        if (var.matches("\\d.*")) {
+        if (STARTS_WITH_DIGIT.matcher(var).matches()) {
             return "_" + var;
         } else {
             return var;
@@ -1350,14 +1350,14 @@ public String toVarName(String name) {
         name = sanitizeName(name);
 
         // if it's all upper case, do nothing
-        if (name.matches("^[A-Z_]*$")) {
+        if (ALL_UPPER_UNDERSCORE.matcher(name).matches()) {
             return name;
         }
 
         name = getNameUsingModelPropertyNaming(name);
 
         // for reserved word or word starting with number, append _
-        if (isReservedWord(name) || name.matches("^\\d.*")) {
+        if (isReservedWord(name) || STARTS_WITH_DIGIT.matcher(name).matches()) {
             name = escapeReservedWord(name);
         }
 
diff --git a/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/CSharpReducedClientCodegen.java b/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/CSharpReducedClientCodegen.java
index 99ba87ce923e..72663fbce843 100644
--- a/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/CSharpReducedClientCodegen.java
+++ b/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/CSharpReducedClientCodegen.java
@@ -840,18 +840,18 @@ public String toEnumVarName(String value, String datatype) {
         if (datatype.startsWith("int") || datatype.startsWith("long") ||
                 datatype.startsWith("double") || datatype.startsWith("float")) {
             String varName = "NUMBER_" + value;
-            varName = varName.replaceAll("-", "MINUS_");
-            varName = varName.replaceAll("\\+", "PLUS_");
-            varName = varName.replaceAll("\\.", "_DOT_");
+            varName = MINUS.matcher(varName).replaceAll("MINUS_");
+            varName = PLUS.matcher(varName).replaceAll("PLUS_");
+            varName = DOT.matcher(varName).replaceAll("_DOT_");
             return varName;
         }
 
         // string
-        String var = value.replaceAll(" ", "_");
+        String var = value.replace(" ", "_");
         var = camelize(var);
-        var = var.replaceAll("\\W+", "");
+        var = NON_WORD_PLUS.matcher(var).replaceAll("");
 
-        if (var.matches("\\d.*")) {
+        if (STARTS_WITH_DIGIT.matcher(var).matches()) {
             return "_" + var;
         } else {
             return var;
@@ -874,14 +874,14 @@ public String toVarName(String name) {
         name = sanitizeName(name);
 
         // if it's all upper case, do nothing
-        if (name.matches("^[A-Z_]*$")) {
+        if (ALL_UPPER_UNDERSCORE.matcher(name).matches()) {
             return name;
         }
 
         name = getNameUsingModelPropertyNaming(name);
 
         // for reserved word or word starting with number, append _
-        if (isReservedWord(name) || name.matches("^\\d.*")) {
+        if (isReservedWord(name) || STARTS_WITH_DIGIT.matcher(name).matches()) {
             name = escapeReservedWord(name);
         }
 
diff --git a/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/ClojureClientCodegen.java b/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/ClojureClientCodegen.java
index 08c866a64ef7..4b9de965cfda 100644
--- a/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/ClojureClientCodegen.java
+++ b/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/ClojureClientCodegen.java
@@ -37,6 +37,7 @@
 
 import java.io.File;
 import java.util.*;
+import java.util.regex.Pattern;
 
 import static org.openapitools.codegen.utils.StringUtils.dashize;
 import static org.openapitools.codegen.utils.StringUtils.underscore;
@@ -63,6 +64,9 @@ public class ClojureClientCodegen extends DefaultCodegen implements CodegenConfi
 
     protected String sourceFolder = "src";
 
+    private static final Pattern NON_ALPHA_UNDERSCORE_PLUS = Pattern.compile("[^a-zA-Z_]+");
+    private static final Pattern NON_ALPHANUMERIC_UNDERSCORE_HYPHEN_PLUS = Pattern.compile("[^a-zA-Z0-9_-]+");
+
     public ClojureClientCodegen() {
         super();
 
@@ -306,7 +310,7 @@ public void preprocessOpenAPI(OpenAPI openAPI) {
 
     @Override
     public String sanitizeTag(String tag) {
-        return tag.replaceAll("[^a-zA-Z_]+", "_");
+        return NON_ALPHA_UNDERSCORE_PLUS.matcher(tag).replaceAll("_");
     }
 
     @Override
@@ -359,7 +363,7 @@ public String toVarName(String name) {
             return nameMapping.get(name);
         }
 
-        name = name.replaceAll("[^a-zA-Z0-9_-]+", ""); // FIXME: a parameter should not be assigned. Also declare the methods parameters as 'final'.
+        name = NON_ALPHANUMERIC_UNDERSCORE_HYPHEN_PLUS.matcher(name).replaceAll(""); // FIXME: a parameter should not be assigned. Also declare the methods parameters as 'final'.
         return name;
     }
 
diff --git a/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/CppHttplibServerCodegen.java b/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/CppHttplibServerCodegen.java
index 1056c8b30eb7..7c9a5fe0e92d 100644
--- a/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/CppHttplibServerCodegen.java
+++ b/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/CppHttplibServerCodegen.java
@@ -79,6 +79,17 @@
 public class CppHttplibServerCodegen extends AbstractCppCodegen {
     private final Logger LOGGER = LoggerFactory.getLogger(CppHttplibServerCodegen.class);
 
+    /** Matches a string that consists entirely of uppercase ASCII letters. */
+    private static final java.util.regex.Pattern CPP_ALL_UPPER = java.util.regex.Pattern.compile("[A-Z]+");
+    /** Matches a camelCase boundary for inserting a space separator. */
+    private static final java.util.regex.Pattern CPP_CAMEL_BOUNDARY = java.util.regex.Pattern.compile("([a-z])([A-Z])");
+    /** Matches the last digit-only part of a name after an underscore (e.g. {@code _2} in {@code method_2}). */
+    private static final java.util.regex.Pattern CPP_TRAILING_DIGIT_PART = java.util.regex.Pattern.compile("\\d+");
+    /** Matches a split point at a camelCase boundary OR any non-alphanumeric character. */
+    private static final java.util.regex.Pattern CPP_CAMEL_SPLIT = java.util.regex.Pattern.compile("(?<=[a-z0-9])(?=[A-Z])|[^a-zA-Z0-9]");
+    /** Matches one or more consecutive non-word-and-non-hyphen separators (spaces, underscores, etc.) in a name. */
+    private static final java.util.regex.Pattern CPP_WORD_SEPARATORS = java.util.regex.Pattern.compile("[_\\-\\s]+");
+
     @Override
     public void preprocessOpenAPI(OpenAPI openAPI) {
         super.preprocessOpenAPI(openAPI);
@@ -1315,9 +1326,9 @@ private void processModelVariable(CodegenProperty var, CodegenModel model) {
                     }
                 } else {
                     // Explicit default value from schema - use qualified enum name
-                    String defaultVal = var.defaultValue.replaceAll("\"", "");
+                    String defaultVal = var.defaultValue.replace("\"", "");
                     // Convert numeric enum values (e.g., "100" -> "_100")
-                    if (defaultVal.matches("^[0-9]+$")) {
+                    if (DIGITS_ONLY.matcher(defaultVal).matches()) {
                         defaultVal = "_" + defaultVal;
                     }
                     // Convert to UPPERCASE to match enum definition
@@ -1435,7 +1446,7 @@ public String toModelName(String name) {
             // Try to extract a number suffix for uniqueness
             if (name.contains("_")) {
                 String[] parts = name.split("_");
-                if (parts.length > 1 && parts[parts.length - 1].matches("\\d+")) {
+                if (parts.length > 1 && CPP_TRAILING_DIGIT_PART.matcher(parts[parts.length - 1]).matches()) {
                     return "InlineModel" + parts[parts.length - 1];
                 }
             }
@@ -1828,7 +1839,7 @@ private Map<String, String> stripPathFromClassName(String path) {
                 path = path.replace("_error", "").replace("_Error", "").replace("error_", "").replace("Error_", "");
             }
             // Remove leading underscores
-            String clean = path.replaceAll("^_+", "");
+            String clean = MULTI_LEADING_UNDERSCORES.matcher(path).replaceAll("");
 
             // If the path is now empty or whitespace only, return default
             if (clean.isEmpty() || clean.trim().isEmpty()) {
@@ -1838,7 +1849,7 @@ private Map<String, String> stripPathFromClassName(String path) {
             }
 
             // Split by "/", "_", "-", " ", camelCase boundary
-            String[] segments = clean.split("(?<=[a-z0-9])(?=[A-Z])|[^a-zA-Z0-9]");
+            String[] segments = CPP_CAMEL_SPLIT.split(clean);
             List<String> parts = new ArrayList<>();
             for (String seg : segments) {
                 if (seg != null && !seg.trim().isEmpty()) {
@@ -1940,9 +1951,9 @@ public String toPascalCase(String name) {
         }
 
         // First, insert spaces before uppercase letters to split camelCase
-        String normalized = name.replaceAll("([a-z])([A-Z])", "$1 $2");
+        String normalized = CPP_CAMEL_BOUNDARY.matcher(name).replaceAll("$1 $2");
         // Split on delimiters (hyphens, underscores, spaces)
-        String[] parts = normalized.split("[_\\-\\s]+");
+        String[] parts = CPP_WORD_SEPARATORS.split(normalized);
         StringBuilder result = new StringBuilder();
         for (String part : parts) {
             if (part != null && !part.isEmpty()) {
@@ -2020,7 +2031,7 @@ public String camelize(String name, boolean lowercaseFirstLetter) {
         }
 
         // If the result is the same as input and input is all uppercase,
-        if (result.equals(name) && name.equals(name.toUpperCase(Locale.ROOT)) && name.matches("[A-Z]+")) {
+        if (result.equals(name) && name.equals(name.toUpperCase(Locale.ROOT)) && CPP_ALL_UPPER.matcher(name).matches()) {
             // Handle all-caps words manually
             result = name.substring(0, 1).toUpperCase(Locale.ROOT) + name.substring(1).toLowerCase(Locale.ROOT);
             if (lowercaseFirstLetter) {
@@ -2041,7 +2052,7 @@ public String camelize(String name, boolean lowercaseFirstLetter) {
     public String toHandlerFunctionName(String httpMethod, String path, Boolean prefix) {
         String method = toPascalCase(httpMethod);
         String className = stripPathFromClassName(path).get("className");
-        className = className.replaceAll("[^A-Za-z0-9]", "");
+        className = NON_ALPHANUMERIC_CHAR.matcher(className).replaceAll("");
         if (prefix) {
             return "handle" + method + "For" + toPascalCase(className);
         } else {
@@ -2057,7 +2068,7 @@ public String toHandlerFunctionName(String httpMethod, String path, Boolean pref
      */
     public String toHandlerFunctionRequest(String path, String method) {
         String className = stripPathFromClassName(path).get("className");
-        className = className.replaceAll("[^A-Za-z0-9]", "");
+        className = NON_ALPHANUMERIC_CHAR.matcher(className).replaceAll("");
         return toPascalCase(className + toPascalCase(method) + "Request");
     }
 
@@ -2070,7 +2081,7 @@ public String toHandlerFunctionRequest(String path, String method) {
      */
     public String toHandlerFunctionResponse(String path, String method) {
         String className = stripPathFromClassName(path).get("className");
-        className = className.replaceAll("[^A-Za-z0-9]", "");
+        className = NON_ALPHANUMERIC_CHAR.matcher(className).replaceAll("");
         return toPascalCase(className + toPascalCase(method) + "Response");
     }
 
@@ -2374,7 +2385,7 @@ private void convertNumericEnumValues(CodegenProperty property) {
                 String enumValStr = enumVal != null ? enumVal.toString() : "";
                 String convertedVal = enumValStr;
                 // Convert numeric values to have underscore prefix
-                if (enumValStr.matches("^[0-9]+$")) {
+                if (DIGITS_ONLY.matcher(enumValStr).matches()) {
                     convertedVal = "_" + enumValStr;
                 }
                 // Convert to UPPERCASE for C++ enum standards (clang style)
@@ -2457,7 +2468,7 @@ private void setEnumVendorExtensions(Object varObj, CodegenModel model) {
             for (String enumVal : enumValues) {
                 // Convert numeric values to words or keep string values as-is
                 String convertedVal = enumVal;
-                if (enumVal.matches("^[0-9]+$")) {
+                if (DIGITS_ONLY.matcher(enumVal).matches()) {
                     // Convert number to enum name
                     convertedVal = "_" + enumVal;  // Prefix with underscore for numeric values
                 }
diff --git a/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/CppOatppClientCodegen.java b/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/CppOatppClientCodegen.java
index eec28ac05de1..20f8b9da773e 100644
--- a/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/CppOatppClientCodegen.java
+++ b/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/CppOatppClientCodegen.java
@@ -155,10 +155,10 @@ public void processOpts() {
             reservedWordPrefix = (String) additionalProperties.get(RESERVED_WORD_PREFIX_OPTION);
         }
 
-        additionalProperties.put("modelNamespaceDeclarations", modelPackage.split("\\."));
-        additionalProperties.put("modelNamespace", modelPackage.replaceAll("\\.", "::"));
-        additionalProperties.put("apiNamespaceDeclarations", apiPackage.split("\\."));
-        additionalProperties.put("apiNamespace", apiPackage.replaceAll("\\.", "::"));
+        additionalProperties.put("modelNamespaceDeclarations", DOT.split(modelPackage));
+        additionalProperties.put("modelNamespace", DOT.matcher(modelPackage).replaceAll("::"));
+        additionalProperties.put("apiNamespaceDeclarations", DOT.split(apiPackage));
+        additionalProperties.put("apiNamespace", DOT.matcher(apiPackage).replaceAll("::"));
         additionalProperties.put(RESERVED_WORD_PREFIX_OPTION, reservedWordPrefix);
 
         if (additionalProperties.containsKey(OPTIONAL_EXTERNAL_LIB)) {
@@ -219,7 +219,7 @@ public CodegenOperation fromOperation(String path, String httpMethod, Operation
             }
         }
 
-        String pathForOatpp = path.replaceAll("\\{(.*?)}", "{$1}");
+        String pathForOatpp = PATH_PARAMETER.matcher(path).replaceAll("{$1}");
         op.vendorExtensions.put("x-codegen-oatpp-path", pathForOatpp);
 
         return op;
diff --git a/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/CppOatppServerCodegen.java b/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/CppOatppServerCodegen.java
index d4d1a33fb7d1..48921ab8ccc3 100644
--- a/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/CppOatppServerCodegen.java
+++ b/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/CppOatppServerCodegen.java
@@ -158,10 +158,10 @@ public void processOpts() {
             reservedWordPrefix = (String) additionalProperties.get(RESERVED_WORD_PREFIX_OPTION);
         }
 
-        additionalProperties.put("modelNamespaceDeclarations", modelPackage.split("\\."));
-        additionalProperties.put("modelNamespace", modelPackage.replaceAll("\\.", "::"));
-        additionalProperties.put("apiNamespaceDeclarations", apiPackage.split("\\."));
-        additionalProperties.put("apiNamespace", apiPackage.replaceAll("\\.", "::"));
+        additionalProperties.put("modelNamespaceDeclarations", DOT.split(modelPackage));
+        additionalProperties.put("modelNamespace", DOT.matcher(modelPackage).replaceAll("::"));
+        additionalProperties.put("apiNamespaceDeclarations", DOT.split(apiPackage));
+        additionalProperties.put("apiNamespace", DOT.matcher(apiPackage).replaceAll("::"));
         additionalProperties.put(RESERVED_WORD_PREFIX_OPTION, reservedWordPrefix);
 
         if (additionalProperties.containsKey(OPTIONAL_EXTERNAL_LIB)) {
@@ -222,7 +222,7 @@ public CodegenOperation fromOperation(String path, String httpMethod, Operation
             }
         }
 
-        String pathForOatpp = path.replaceAll("\\{(.*?)}", "{$1}");
+        String pathForOatpp = PATH_PARAMETER.matcher(path).replaceAll("{$1}");
         op.vendorExtensions.put("x-codegen-oatpp-path", pathForOatpp);
 
         return op;
diff --git a/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/CppPistacheServerCodegen.java b/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/CppPistacheServerCodegen.java
index b740e50db0a9..1adf24d01906 100644
--- a/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/CppPistacheServerCodegen.java
+++ b/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/CppPistacheServerCodegen.java
@@ -213,12 +213,12 @@ public void processOpts() {
             reservedWordPrefix = (String) additionalProperties.get(RESERVED_WORD_PREFIX_OPTION);
         }
 
-        additionalProperties.put("modelNamespaceDeclarations", modelPackage.split("\\."));
-        additionalProperties.put("modelNamespace", modelPackage.replaceAll("\\.", "::"));
-        additionalProperties.put("apiNamespaceDeclarations", apiPackage.split("\\."));
-        additionalProperties.put("apiNamespace", apiPackage.replaceAll("\\.", "::"));
-        additionalProperties.put("helpersNamespaceDeclarations", helpersPackage.split("\\."));
-        additionalProperties.put("helpersNamespace", helpersPackage.replaceAll("\\.", "::"));
+        additionalProperties.put("modelNamespaceDeclarations", DOT.split(modelPackage));
+        additionalProperties.put("modelNamespace", DOT.matcher(modelPackage).replaceAll("::"));
+        additionalProperties.put("apiNamespaceDeclarations", DOT.split(apiPackage));
+        additionalProperties.put("apiNamespace", DOT.matcher(apiPackage).replaceAll("::"));
+        additionalProperties.put("helpersNamespaceDeclarations", DOT.split(helpersPackage));
+        additionalProperties.put("helpersNamespace", DOT.matcher(helpersPackage).replaceAll("::"));
         additionalProperties.put(RESERVED_WORD_PREFIX_OPTION, reservedWordPrefix);
 
         if (additionalProperties.containsKey(OPTIONAL_EXTERNAL_LIB)) {
@@ -309,7 +309,7 @@ public CodegenOperation fromOperation(String path, String httpMethod, Operation
             }
         }
 
-        String pathForPistache = path.replaceAll("\\{(.*?)}", ":$1");
+        String pathForPistache = PATH_PARAMETER.matcher(path).replaceAll(":$1");
         op.vendorExtensions.put("x-codegen-pistache-path", pathForPistache);
 
         return op;
diff --git a/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/CppQtAbstractCodegen.java b/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/CppQtAbstractCodegen.java
index 82f87d6b8008..758e66fe19fe 100644
--- a/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/CppQtAbstractCodegen.java
+++ b/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/CppQtAbstractCodegen.java
@@ -304,7 +304,7 @@ public String toVarName(String name) {
         varName = sanitizeName(name);
 
         // if it's all upper case, convert to lower case
-        if (varName.matches("^[A-Z_]*$")) {
+        if (ALL_UPPER_UNDERSCORE.matcher(varName).matches()) {
             varName = varName.toLowerCase(Locale.ROOT);
         }
 
@@ -313,7 +313,7 @@ public String toVarName(String name) {
         varName = org.openapitools.codegen.utils.StringUtils.underscore(varName);
 
         // for reserved word or word starting with number, append _
-        if (isReservedWord(varName) || varName.matches("^\\d.*")) {
+        if (isReservedWord(varName) || STARTS_WITH_DIGIT.matcher(varName).matches()) {
             varName = escapeReservedWord(varName);
         }
 
diff --git a/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/CppRestSdkClientCodegen.java b/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/CppRestSdkClientCodegen.java
index 5a8e523cf513..f3c449e36f5b 100644
--- a/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/CppRestSdkClientCodegen.java
+++ b/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/CppRestSdkClientCodegen.java
@@ -207,12 +207,12 @@ public void processOpts() {
         }
 
         additionalProperties.put(CodegenConstants.PACKAGE_NAME, packageName);
-        additionalProperties.put("modelNamespaceDeclarations", modelPackage.split("\\."));
-        additionalProperties.put("modelNamespace", modelPackage.replaceAll("\\.", "::"));
-        additionalProperties.put("modelHeaderGuardPrefix", modelPackage.replaceAll("\\.", "_").toUpperCase(Locale.ROOT));
-        additionalProperties.put("apiNamespaceDeclarations", apiPackage.split("\\."));
-        additionalProperties.put("apiNamespace", apiPackage.replaceAll("\\.", "::"));
-        additionalProperties.put("apiHeaderGuardPrefix", apiPackage.replaceAll("\\.", "_").toUpperCase(Locale.ROOT));
+        additionalProperties.put("modelNamespaceDeclarations", DOT.split(modelPackage));
+        additionalProperties.put("modelNamespace", DOT.matcher(modelPackage).replaceAll("::"));
+        additionalProperties.put("modelHeaderGuardPrefix", DOT.matcher(modelPackage).replaceAll("_").toUpperCase(Locale.ROOT));
+        additionalProperties.put("apiNamespaceDeclarations", DOT.split(apiPackage));
+        additionalProperties.put("apiNamespace", DOT.matcher(apiPackage).replaceAll("::"));
+        additionalProperties.put("apiHeaderGuardPrefix", DOT.matcher(apiPackage).replaceAll("_").toUpperCase(Locale.ROOT));
         additionalProperties.put("declspec", declspec);
         additionalProperties.put("defaultInclude", defaultInclude);
         additionalProperties.put(RESERVED_WORD_PREFIX_OPTION, reservedWordPrefix);
diff --git a/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/CppRestbedServerCodegen.java b/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/CppRestbedServerCodegen.java
index bf2054e472c7..a7d3994c7304 100644
--- a/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/CppRestbedServerCodegen.java
+++ b/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/CppRestbedServerCodegen.java
@@ -231,10 +231,10 @@ public void processOpts() {
             reservedWordPrefix = additionalProperties.get(RESERVED_WORD_PREFIX_OPTION).toString();
         }
 
-        additionalProperties.put("modelNamespaceDeclarations", modelPackage.split("\\."));
-        additionalProperties.put("modelNamespace", modelPackage.replaceAll("\\.", "::"));
-        additionalProperties.put("apiNamespaceDeclarations", apiPackage.split("\\."));
-        additionalProperties.put("apiNamespace", apiPackage.replaceAll("\\.", "::"));
+        additionalProperties.put("modelNamespaceDeclarations", DOT.split(modelPackage));
+        additionalProperties.put("modelNamespace", DOT.matcher(modelPackage).replaceAll("::"));
+        additionalProperties.put("apiNamespaceDeclarations", DOT.split(apiPackage));
+        additionalProperties.put("apiNamespace", DOT.matcher(apiPackage).replaceAll("::"));
         additionalProperties.put("declspec", declspec);
         additionalProperties.put("defaultInclude", defaultInclude);
         additionalProperties.put(RESERVED_WORD_PREFIX_OPTION, reservedWordPrefix);
diff --git a/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/CppRestbedServerDeprecatedCodegen.java b/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/CppRestbedServerDeprecatedCodegen.java
index 603e81e00308..c43fae3ac508 100644
--- a/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/CppRestbedServerDeprecatedCodegen.java
+++ b/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/CppRestbedServerDeprecatedCodegen.java
@@ -218,10 +218,10 @@ public void processOpts() {
             reservedWordPrefix = additionalProperties.get(RESERVED_WORD_PREFIX_OPTION).toString();
         }
 
-        additionalProperties.put("modelNamespaceDeclarations", modelPackage.split("\\."));
-        additionalProperties.put("modelNamespace", modelPackage.replaceAll("\\.", "::"));
-        additionalProperties.put("apiNamespaceDeclarations", apiPackage.split("\\."));
-        additionalProperties.put("apiNamespace", apiPackage.replaceAll("\\.", "::"));
+        additionalProperties.put("modelNamespaceDeclarations", DOT.split(modelPackage));
+        additionalProperties.put("modelNamespace", DOT.matcher(modelPackage).replaceAll("::"));
+        additionalProperties.put("apiNamespaceDeclarations", DOT.split(apiPackage));
+        additionalProperties.put("apiNamespace", DOT.matcher(apiPackage).replaceAll("::"));
         additionalProperties.put("declspec", declspec);
         additionalProperties.put("defaultInclude", defaultInclude);
         additionalProperties.put(RESERVED_WORD_PREFIX_OPTION, reservedWordPrefix);
diff --git a/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/CppTinyClientCodegen.java b/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/CppTinyClientCodegen.java
index 7c55e0fbb24b..8f84f08b493c 100644
--- a/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/CppTinyClientCodegen.java
+++ b/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/CppTinyClientCodegen.java
@@ -337,8 +337,8 @@ public String toApiImport(String name) {
 
     @Override
     public String toVarName(String name) {
-        String paramName = name.replaceAll("[^a-zA-Z0-9_]", "");
-        if (name.length() > 0) {
+        String paramName = NON_WORD_CHAR.matcher(name).replaceAll("");
+        if (!name.isEmpty()) {
             paramName = Character.toLowerCase(paramName.charAt(0)) + paramName.substring(1);
         }
         if (isReservedWord(paramName)) {
diff --git a/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/CppTizenClientCodegen.java b/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/CppTizenClientCodegen.java
index 9341df65be7d..36c36a87f92b 100644
--- a/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/CppTizenClientCodegen.java
+++ b/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/CppTizenClientCodegen.java
@@ -288,8 +288,8 @@ public String toApiFilename(String name) {
 
     @Override
     public String toVarName(String name) {
-        String paramName = name.replaceAll("[^a-zA-Z0-9_]", "");
-        if (name.length() > 0) {
+        String paramName = NON_WORD_CHAR.matcher(name).replaceAll("");
+        if (!name.isEmpty()) {
             // additionalProperties name is "" so name.length() == 0
             paramName = Character.toLowerCase(paramName.charAt(0)) + paramName.substring(1);
         }
diff --git a/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/CppUE4ClientCodegen.java b/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/CppUE4ClientCodegen.java
index 13ab898fa39a..736461fc5797 100644
--- a/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/CppUE4ClientCodegen.java
+++ b/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/CppUE4ClientCodegen.java
@@ -516,7 +516,7 @@ public String toVarName(String name) {
         name = sanitizeName(name); // FIXME: a parameter should not be assigned. Also declare the methods parameters as 'final'.
 
         // if it's all upper case, convert to lower case
-        if (name.matches("^[A-Z_]*$")) {
+        if (ALL_UPPER_UNDERSCORE.matcher(name).matches()) {
             name = name.toLowerCase(Locale.ROOT);
         }
 
@@ -529,7 +529,7 @@ public String toVarName(String name) {
         }
 
         // for reserved word or word starting with number, append _
-        if (isReservedWord(name) || name.matches("^\\d.*")) {
+        if (isReservedWord(name) || STARTS_WITH_DIGIT.matcher(name).matches()) {
             name = escapeReservedWord(name);
         }
 
diff --git a/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/CrystalClientCodegen.java b/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/CrystalClientCodegen.java
index 29bb9e09ab95..ecc1faeb3c53 100644
--- a/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/CrystalClientCodegen.java
+++ b/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/CrystalClientCodegen.java
@@ -407,7 +407,7 @@ public String toModelName(final String name) {
         }
 
         // model name starts with number
-        if (modelName.matches("^\\d.*")) {
+        if (STARTS_WITH_DIGIT.matcher(modelName).matches()) {
             LOGGER.warn("{} (model name starts with number) cannot be used as model name. Renamed to {}", modelName, camelize("model_" + modelName));
             // e.g. 200Response => Model200Response (after camelize)
             modelName = "model_" + modelName;
@@ -450,7 +450,7 @@ public String toApiFilename(final String name) {
             filename = filename + "_" + apiNameSuffix;
         }
 
-        filename = filename.replaceAll("-", "_");
+        filename = MINUS.matcher(filename).replaceAll("_");
 
         // e.g. PhoneNumberApi.cr => phone_number_api.cr
         return underscore(filename);
@@ -494,18 +494,18 @@ public String toEnumVarName(String name, String datatype) {
         // number
         if ("Integer".equals(datatype) || "Float".equals(datatype)) {
             String varName = name;
-            varName = varName.replaceAll("-", "MINUS_");
-            varName = varName.replaceAll("\\+", "PLUS_");
-            varName = varName.replaceAll("\\.", "_DOT_");
+            varName = MINUS.matcher(varName).replaceAll("MINUS_");
+            varName = PLUS.matcher(varName).replaceAll("PLUS_");
+            varName = DOT.matcher(varName).replaceAll("_DOT_");
             return NUMERIC_ENUM_PREFIX + varName;
         }
 
         // string
         String enumName = sanitizeName(underscore(name).toUpperCase(Locale.ROOT));
-        enumName = enumName.replaceFirst("^_", "");
-        enumName = enumName.replaceFirst("_$", "");
+        enumName = FIRST_LEADING_UNDERSCORE.matcher(enumName).replaceFirst("");
+        enumName = LAST_TRAILING_UNDERSCORE.matcher(enumName).replaceFirst("");
 
-        if (enumName.matches("\\d.*")) { // starts with number
+        if (STARTS_WITH_DIGIT.matcher(enumName).matches()) { // starts with number
             return NUMERIC_ENUM_PREFIX + enumName;
         } else {
             return enumName;
@@ -515,10 +515,10 @@ public String toEnumVarName(String name, String datatype) {
     @Override
     public String toEnumName(CodegenProperty property) {
         String enumName = underscore(toModelName(property.name)).toUpperCase(Locale.ROOT);
-        enumName = enumName.replaceFirst("^_", "");
-        enumName = enumName.replaceFirst("_$", "");
+        enumName = FIRST_LEADING_UNDERSCORE.matcher(enumName).replaceFirst("");
+        enumName = LAST_TRAILING_UNDERSCORE.matcher(enumName).replaceFirst("");
 
-        if (enumName.matches("\\d.*")) { // starts with number
+        if (STARTS_WITH_DIGIT.matcher(enumName).matches()) { // starts with number
             return NUMERIC_ENUM_PREFIX + enumName;
         } else {
             return enumName;
@@ -548,7 +548,7 @@ public String toOperationId(String operationId) {
         }
 
         // operationId starts with a number
-        if (operationId.matches("^\\d.*")) {
+        if (STARTS_WITH_DIGIT.matcher(operationId).matches()) {
             LOGGER.warn("{} (starting with a number) cannot be used as method name. Renamed to {}", operationId, underscore(sanitizeName("call_" + operationId)));
             operationId = "call_" + operationId;
         }
@@ -871,7 +871,7 @@ public String toVarName(final String name) {
         // sanitize name
         varName = sanitizeName(name);
         // if it's all upper case, convert to lower case
-        if (name.matches("^[A-Z_]*$")) {
+        if (ALL_UPPER_UNDERSCORE.matcher(name).matches()) {
             varName = varName.toLowerCase(Locale.ROOT);
         }
 
@@ -880,7 +880,7 @@ public String toVarName(final String name) {
         varName = underscore(varName);
 
         // for reserved word or word starting with number, append _
-        if (isReservedWord(varName) || varName.matches("^\\d.*")) {
+        if (isReservedWord(varName) || STARTS_WITH_DIGIT.matcher(varName).matches()) {
             varName = escapeReservedWord(varName);
         }
 
diff --git a/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/EiffelClientCodegen.java b/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/EiffelClientCodegen.java
index af66fcf53e39..b42dc64651f9 100644
--- a/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/EiffelClientCodegen.java
+++ b/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/EiffelClientCodegen.java
@@ -212,15 +212,15 @@ public String toEnumVarName(String value, String datatype) {
         if ("INTEGER_32".equals(datatype) || "INTEGER_64".equals(datatype) ||
                 "REAL_32".equals(datatype) || "REAL_64".equals(datatype)) {
             String varName = "NUMBER_" + value;
-            varName = varName.replaceAll("-", "MINUS_");
-            varName = varName.replaceAll("\\+", "PLUS_");
-            varName = varName.replaceAll("\\.", "_DOT_");
+            varName = MINUS.matcher(varName).replaceAll("MINUS_");
+            varName = PLUS.matcher(varName).replaceAll("PLUS_");
+            varName = DOT.matcher(varName).replaceAll("_DOT_");
             return varName;
         }
 
         // string
-        String var = value.replaceAll("\\W+", "_").toLowerCase(Locale.ROOT);
-        if (var.matches("\\d.*")) {
+        String var = NON_WORD_PLUS.matcher(value).replaceAll("_").toLowerCase(Locale.ROOT);
+        if (STARTS_WITH_DIGIT.matcher(var).matches()) {
             return "val_" + var;
         } else if (var.startsWith("_")) {
             return "val" + var;
diff --git a/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/ElixirClientCodegen.java b/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/ElixirClientCodegen.java
index c68ad41f8a08..e6245618f081 100644
--- a/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/ElixirClientCodegen.java
+++ b/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/ElixirClientCodegen.java
@@ -48,6 +48,7 @@
 public class ElixirClientCodegen extends DefaultCodegen {
     private final Logger LOGGER = LoggerFactory.getLogger(ElixirClientCodegen.class);
 
+    private static final Pattern PATH_TEMPLATE_PATTERN = Pattern.compile("\\{([^\\}]+)\\}([^\\{]*)");
     private final Pattern simpleAtomPattern = Pattern.compile("\\A(?:(?:[_\\p{Alpha}][_@\\p{Alnum}]*[?!]?)|-|@)\\z");
 
     @Setter protected String packageVersion = "1.0.0";
@@ -348,10 +349,9 @@ public OperationsMap postProcessOperationsWithModels(OperationsMap objs, List<Mo
         OperationMap operations = super.postProcessOperationsWithModels(objs, allModels).getOperations();
         List<CodegenOperation> os = operations.getOperation();
         List<ExtendedCodegenOperation> newOs = new ArrayList<>();
-        Pattern pattern = Pattern.compile("\\{([^\\}]+)\\}([^\\{]*)");
         for (CodegenOperation o : os) {
             ArrayList<String> pathTemplateNames = new ArrayList<>();
-            Matcher matcher = pattern.matcher(o.path);
+            Matcher matcher = PATH_TEMPLATE_PATTERN.matcher(o.path);
             StringBuffer buffer = new StringBuffer();
             while (matcher.find()) {
                 String pathTemplateName = matcher.group(1);
@@ -453,13 +453,13 @@ public String escapeReservedWord(String name) {
         String escapedName = name + "_var";
 
         // Trim leading underscores in the event the name is already underscored
-        escapedName = escapedName.replaceAll("^_+", "");
+        escapedName = MULTI_LEADING_UNDERSCORES.matcher(escapedName).replaceAll("");
         return escapedName;
     }
 
     private String sourceFolder() {
         ArrayList<String> underscoredWords = new ArrayList<>();
-        for (String word : moduleName.split("\\.")) {
+        for (String word : DOT.split(moduleName)) {
             underscoredWords.add(underscore(word));
         }
         return ("lib/" + join("/", underscoredWords)).replace('/', File.separatorChar);
@@ -496,7 +496,7 @@ public String toApiName(String name) {
     @Override
     public String toApiFilename(String name) {
         // replace - with _ e.g. created-at => created_at
-        name = name.replaceAll("-", "_");
+        name = MINUS.matcher(name).replaceAll("_");
 
         // e.g. PetApi.go => pet_api.go
         return underscore(name);
@@ -539,7 +539,7 @@ public String toModelFilename(String name) {
         }
 
         // model name starts with number
-        if (name.matches("^\\d.*")) {
+        if (STARTS_WITH_DIGIT.matcher(name).matches()) {
             LOGGER.warn("{} (model name starts with number) cannot be used as model name. Renamed to {}", name,
                     "model_" + name);
             name = "model_" + name; // e.g. 200Response => Model200Response (after camelize)
@@ -564,7 +564,7 @@ public String toOperationId(String operationId) {
         }
 
         // operationId starts with a number
-        if (operationId.matches("^\\d.*")) {
+        if (STARTS_WITH_DIGIT.matcher(operationId).matches()) {
             LOGGER.warn("{} (starting with a number) cannot be used as method name. Renamed to {}", operationId,
                     underscore(sanitizeName("call_" + operationId)));
             operationId = "call_" + operationId;
diff --git a/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/ElmClientCodegen.java b/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/ElmClientCodegen.java
index ed17189a1fd3..dd4af3368573 100644
--- a/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/ElmClientCodegen.java
+++ b/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/ElmClientCodegen.java
@@ -198,7 +198,7 @@ public String toOperationId(String operationId) {
         }
 
         // operationId starts with a number
-        if (operationId.matches("^\\d.*")) {
+        if (STARTS_WITH_DIGIT.matcher(operationId).matches()) {
             LOGGER.warn(operationId + " (starting with a number) cannot be used as method sname. Renamed to " + camelize("call_" + operationId), true);
             operationId = camelize("call_" + operationId, LOWERCASE_FIRST_LETTER);
         }
@@ -228,7 +228,7 @@ public String toEnumName(CodegenProperty property) {
     @Override
     public String toVarName(String name) {
         // Replace space with _ (underscore) so camelize works as expected
-        final String varName = camelize(name.replaceAll(" ", "_").replaceAll("[^a-zA-Z0-9_]", ""),
+        final String varName = camelize(NON_WORD_CHAR.matcher(name.replace(" ", "_")).replaceAll(""),
                 LOWERCASE_FIRST_LETTER);
         return isReservedWord(varName) ? escapeReservedWord(name) : varName;
     }
@@ -490,7 +490,7 @@ public String getTypeDeclaration(Schema p) {
     private static class RemoveWhitespaceLambda implements Mustache.Lambda {
         @Override
         public void execute(final Template.Fragment fragment, final Writer writer) throws IOException {
-            writer.write(fragment.execute().replaceAll("\\s+", " ").trim());
+            writer.write(WHITESPACE.matcher(fragment.execute()).replaceAll(" ").trim());
         }
     }
 
diff --git a/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/ErlangClientCodegen.java b/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/ErlangClientCodegen.java
index a596660a9c60..643d34541221 100644
--- a/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/ErlangClientCodegen.java
+++ b/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/ErlangClientCodegen.java
@@ -44,8 +44,12 @@
 public class ErlangClientCodegen extends DefaultCodegen implements CodegenConfig {
     private final Logger LOGGER = LoggerFactory.getLogger(ErlangClientCodegen.class);
 
-    @Setter protected String packageName = "openapi";
-    @Setter protected String packageVersion = "1.0.0";
+    private static final Pattern PATH_TEMPLATE_PATTERN = Pattern.compile("\\{([^\\}]+)\\}");
+
+    @Setter
+    protected String packageName = "openapi";
+    @Setter
+    protected String packageVersion = "1.0.0";
     protected String sourceFolder = "src";
 
     @Override
@@ -256,7 +260,7 @@ public String toVarName(String name) {
         }
 
         // replace - with _ e.g. created-at => created_at
-        name = sanitizeName(name.replaceAll("-", "_"));
+        name = sanitizeName(MINUS.matcher(name).replaceAll("_"));
         // for reserved word or word starting with number, append _
         if (isReservedWord(name))
             name = escapeReservedWord(name);
@@ -289,24 +293,24 @@ public String toArrayModelParamName(String name) {
 
     @Override
     public String toModelName(String name) {
-        return this.packageName + "_" + underscore(name.replaceAll("-", "_").replaceAll("\\.", "_"));
+        return this.packageName + "_" + underscore(DOT.matcher(MINUS.matcher(name).replaceAll("_")).replaceAll("_"));
     }
 
     @Override
     public String toApiName(String name) {
-        return this.packageName + "_" + underscore(name.replaceAll("-", "_").replaceAll("\\.", "_"));
+        return this.packageName + "_" + underscore(DOT.matcher(MINUS.matcher(name).replaceAll("_")).replaceAll("_"));
     }
 
     @Override
     public String toModelFilename(String name) {
-        return this.packageName + "_" + underscore(name.replaceAll("\\.", "_"));
+        return this.packageName + "_" + underscore(DOT.matcher(name).replaceAll("_"));
     }
 
     @Override
     public String toApiFilename(String name) {
         // replace - with _ e.g. created-at => created_at
         // FIXME: a parameter should not be assigned. Also declare the methods parameters as 'final'.
-        name = name.replaceAll("-", "_").replaceAll("\\.", "_");
+        name = DOT.matcher(MINUS.matcher(name).replaceAll("_")).replaceAll("_");
 
         // e.g. PetApi.erl => pet_api.erl
         return this.packageName + "_" + underscore(name) + "_api";
@@ -316,11 +320,11 @@ public String toApiFilename(String name) {
     public String toOperationId(String operationId) {
         // method name cannot use reserved keyword, e.g. if
         if (isReservedWord(operationId)) {
-            LOGGER.warn("{} (reserved word) cannot be used as method name. Renamed to {}", operationId, underscore(sanitizeName("call_" + operationId)).replaceAll("\\.", "_"));
+            LOGGER.warn("{} (reserved word) cannot be used as method name. Renamed to {}", operationId, DOT.matcher(underscore(sanitizeName("call_" + operationId))).replaceAll("_"));
             operationId = "call_" + operationId;
         }
 
-        return underscore(operationId.replaceAll("\\.", "_"));
+        return underscore(DOT.matcher(operationId).replaceAll("_"));
     }
 
     @Override
@@ -328,7 +332,6 @@ public OperationsMap postProcessOperationsWithModels(OperationsMap objs, List<Mo
         OperationMap operations = objs.getOperations();
         List<CodegenOperation> os = operations.getOperation();
         List<ExtendedCodegenOperation> newOs = new ArrayList<>();
-        Pattern pattern = Pattern.compile("\\{([^\\}]+)\\}");
         for (CodegenOperation o : os) {
             // force http method to lower case
             o.httpMethod = o.httpMethod.toLowerCase(Locale.ROOT);
@@ -338,7 +341,7 @@ public OperationsMap postProcessOperationsWithModels(OperationsMap objs, List<Mo
             }
 
             ArrayList<String> pathTemplateNames = new ArrayList<>();
-            Matcher matcher = pattern.matcher(o.path);
+            Matcher matcher = PATH_TEMPLATE_PATTERN.matcher(o.path);
             StringBuffer buffer = new StringBuffer();
             while (matcher.find()) {
                 String pathTemplateName = matcher.group(1);
@@ -402,9 +405,11 @@ public String escapeUnsafeCharacters(String input) {
     }
 
     class ExtendedCodegenOperation extends CodegenOperation {
-        @Getter @Setter
+        @Getter
+        @Setter
         private List<String> pathTemplateNames = new ArrayList<String>();
-        @Getter @Setter
+        @Getter
+        @Setter
         private String replacedPathName;
         String arityRequired;
         String arityOptional;
diff --git a/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/ErlangProperCodegen.java b/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/ErlangProperCodegen.java
index c9ce46417995..05179e0c20e5 100644
--- a/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/ErlangProperCodegen.java
+++ b/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/ErlangProperCodegen.java
@@ -311,7 +311,7 @@ public String modelFileFolder() {
     @Override
     public String toVarName(String name) {
         // replace - with _ e.g. created-at => created_at
-        name = sanitizeName(name.replaceAll("-", "_"));
+        name = sanitizeName(MINUS.matcher(name).replaceAll("_"));
         // for reserved word or word starting with number, append _
         if (isReservedWord(name))
             name = escapeReservedWord(name);
@@ -340,7 +340,7 @@ public String toArrayModelParamName(String name) {
 
     @Override
     public String toModelName(String name) {
-        return this.packageName + "_" + underscore(name.replaceAll("-", "_").replaceAll("\\.", "_"));
+        return this.packageName + "_" + underscore(DOT.matcher(MINUS.matcher(name).replaceAll("_")).replaceAll("_"));
     }
 
     @Override
@@ -350,7 +350,7 @@ public String toApiName(String name) {
 
     @Override
     public String toModelFilename(String name) {
-        return this.packageName + "_" + underscore(name.replaceAll("\\.", "_"));
+        return this.packageName + "_" + underscore(DOT.matcher(name).replaceAll("_"));
     }
 
     @Override
@@ -362,11 +362,11 @@ public String toApiFilename(String name) {
     public String toOperationId(String operationId) {
         // method name cannot use reserved keyword, e.g. return
         if (isReservedWord(operationId)) {
-            LOGGER.warn("{} (reserved word) cannot be used as method name. Renamed to {}", operationId, underscore(sanitizeName("call_" + operationId)).replaceAll("\\.", "_"));
+            LOGGER.warn("{} (reserved word) cannot be used as method name. Renamed to {}", operationId, DOT.matcher(underscore(sanitizeName("call_" + operationId))).replaceAll("_"));
             operationId = "call_" + operationId;
         }
 
-        return underscore(operationId.replaceAll("\\.", "_"));
+        return underscore(DOT.matcher(operationId).replaceAll("_"));
     }
 
     @Override
diff --git a/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/ErlangServerCodegen.java b/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/ErlangServerCodegen.java
index 4581e6e4509f..b4b246bbf575 100644
--- a/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/ErlangServerCodegen.java
+++ b/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/ErlangServerCodegen.java
@@ -276,7 +276,7 @@ public OperationsMap postProcessOperationsWithModels(OperationsMap objs, List<Mo
         List<CodegenOperation> operationList = operations.getOperation();
         for (CodegenOperation op : operationList) {
             if (op.path != null) {
-                op.path = op.path.replaceAll("\\{(.*?)\\}", ":$1");
+                op.path = PATH_PARAMETER.matcher(op.path).replaceAll(":$1");
             }
         }
         return objs;
@@ -293,7 +293,7 @@ protected String toHandlerName(String name) {
     }
 
     protected String toModuleName(String name) {
-        return this.packageName + "_" + underscore(name.replaceAll("-", "_"));
+        return this.packageName + "_" + underscore(MINUS.matcher(name).replaceAll("_"));
     }
 
     protected String toSourceFilePath(String name, String extension) {
diff --git a/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/ErlangServerDeprecatedCodegen.java b/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/ErlangServerDeprecatedCodegen.java
index c0e0e60a32c4..2d5ff7aa36dc 100644
--- a/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/ErlangServerDeprecatedCodegen.java
+++ b/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/ErlangServerDeprecatedCodegen.java
@@ -282,7 +282,7 @@ public OperationsMap postProcessOperationsWithModels(OperationsMap objs, List<Mo
         List<CodegenOperation> operationList = operations.getOperation();
         for (CodegenOperation op : operationList) {
             if (op.path != null) {
-                op.path = op.path.replaceAll("\\{(.*?)\\}", ":$1");
+                op.path = PATH_PARAMETER.matcher(op.path).replaceAll(":$1");
             }
         }
         return objs;
@@ -299,7 +299,7 @@ protected String toHandlerName(String name) {
     }
 
     protected String toModuleName(String name) {
-        return this.packageName + "_" + underscore(name.replaceAll("-", "_"));
+        return this.packageName + "_" + underscore(MINUS.matcher(name).replaceAll("_"));
     }
 
     protected String toSourceFilePath(String name, String extension) {
diff --git a/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/GdscriptClientCodegen.java b/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/GdscriptClientCodegen.java
index e2e7c5dc2004..e95a4e6d2642 100644
--- a/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/GdscriptClientCodegen.java
+++ b/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/GdscriptClientCodegen.java
@@ -343,9 +343,9 @@ public String escapeReservedWord(String name) {
     }
 
     public String escapeStringLiteral(String input) {
-        return input
-                .replace("\"", "\\\"")  // escape double quotes
-                .replaceAll("[\\\\]+$", "")  // remove trailing backslash(es)
+        return TRAILING_BACKSLASHES.matcher(input
+                .replace("\"", "\\\""))  // escape double quotes
+                .replaceAll("")  // remove trailing backslash(es)
                 // issue: "foo\<control char>" will perhaps still wreak havoc
                 ;
     }
diff --git a/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/GoEchoServerCodegen.java b/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/GoEchoServerCodegen.java
index 621494b0c7a5..c3be9c4ddf5f 100644
--- a/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/GoEchoServerCodegen.java
+++ b/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/GoEchoServerCodegen.java
@@ -118,7 +118,7 @@ public OperationsMap postProcessOperationsWithModels(OperationsMap objs, List<Mo
         List<CodegenOperation> operationList = operations.getOperation();
         for (CodegenOperation op : operationList) {
             if (op.path != null) {
-                op.path = op.path.replaceAll("\\{(.*?)\\}", ":$1");
+                op.path = PATH_PARAMETER.matcher(op.path).replaceAll(":$1");
             }
         }
         return objs;
diff --git a/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/GoGinServerCodegen.java b/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/GoGinServerCodegen.java
index ce8721a251ed..c76e4762fc2b 100644
--- a/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/GoGinServerCodegen.java
+++ b/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/GoGinServerCodegen.java
@@ -133,7 +133,7 @@ public OperationsMap postProcessOperationsWithModels(OperationsMap objs, List<Mo
         List<CodegenOperation> operationList = operations.getOperation();
         for (CodegenOperation op : operationList) {
             if (op.path != null) {
-                op.path = op.path.replaceAll("\\{(.*?)\\}", ":$1");
+                op.path = PATH_PARAMETER.matcher(op.path).replaceAll(":$1");
             }
         }
         return objs;
diff --git a/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/GraphQLNodeJSExpressServerCodegen.java b/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/GraphQLNodeJSExpressServerCodegen.java
index 7bab192f4d50..2f62187e385f 100644
--- a/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/GraphQLNodeJSExpressServerCodegen.java
+++ b/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/GraphQLNodeJSExpressServerCodegen.java
@@ -159,7 +159,7 @@ public String toEnumName(CodegenProperty property) {
         enumName = enumName.replace("[]", "");
 
         // ENUM starts with a number
-        if (enumName.matches("\\d.*")) {
+        if (STARTS_WITH_DIGIT.matcher(enumName).matches()) {
             return StringUtils.capitalize("_" + enumName) + "Enum";
         } else {
             return StringUtils.capitalize(enumName) + "Enum";
diff --git a/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/HaskellHttpClientCodegen.java b/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/HaskellHttpClientCodegen.java
index 00d1a75e9673..0ed1e43aef51 100644
--- a/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/HaskellHttpClientCodegen.java
+++ b/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/HaskellHttpClientCodegen.java
@@ -32,6 +32,7 @@
 import org.openapitools.codegen.model.OperationMap;
 import org.openapitools.codegen.model.OperationsMap;
 import org.openapitools.codegen.utils.ModelUtils;
+import org.openapitools.codegen.utils.PatternCache;
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
 
@@ -49,6 +50,12 @@
 public class HaskellHttpClientCodegen extends DefaultCodegen implements CodegenConfig {
     private final Logger LOGGER = LoggerFactory.getLogger(HaskellHttpClientCodegen.class);
 
+    private static final Pattern XPATH_EMPTY_SEGMENT     = Pattern.compile(",\"\",");
+    private static final Pattern XPATH_LEADING_EMPTY     = Pattern.compile("\"\",");
+    private static final Pattern XPATH_TRAILING_EMPTY    = Pattern.compile(",\"\"");
+    private static final Pattern XPATH_LEADING_COMMA     = Pattern.compile("^\\[,");
+    private static final Pattern XPATH_TRAILING_COMMA    = Pattern.compile(",]$");
+
     // source folder where to write the files
     protected String sourceFolder = "lib";
 
@@ -87,8 +94,6 @@ public class HaskellHttpClientCodegen extends DefaultCodegen implements CodegenC
     // protected String MODEL_IMPORTS = "modelImports";
     // protected String MODEL_EXTENSIONS = "modelExtensions";
 
-    private static final Pattern LEADING_UNDERSCORE = Pattern.compile("^_+");
-
     static final String MEDIA_TYPE = "mediaType";
     static final String MIME_NO_CONTENT = "MimeNoContent";
     static final String MIME_ANY = "MimeAny";
@@ -1059,14 +1064,14 @@ private void processPathExpr(CodegenOperation op) {
         if (op.getHasPathParams()) {
             for (CodegenParameter param : op.allParams) {
                 if (param.isPathParam) {
-                    xPath = xPath.replaceAll("\\{" + param.baseName + "\\}", "\",toPath " + param.paramName + ",\"");
+                    xPath = PatternCache.get("\\{" + param.baseName + "}").matcher(xPath).replaceAll("\",toPath " + param.paramName + ",\"");
                 }
             }
-            xPath = xPath.replaceAll(",\"\",", ",");
-            xPath = xPath.replaceAll("\"\",", ",");
-            xPath = xPath.replaceAll(",\"\"", ",");
-            xPath = xPath.replaceAll("^\\[,", "[");
-            xPath = xPath.replaceAll(",\\]$", "]");
+            xPath = XPATH_EMPTY_SEGMENT.matcher(xPath).replaceAll(",");
+            xPath = XPATH_LEADING_EMPTY.matcher(xPath).replaceAll(",");
+            xPath = XPATH_TRAILING_EMPTY.matcher(xPath).replaceAll(",");
+            xPath = XPATH_LEADING_COMMA.matcher(xPath).replaceAll("[");
+            xPath = XPATH_TRAILING_COMMA.matcher(xPath).replaceAll("]");
         }
         op.vendorExtensions.put(VENDOR_EXTENSION_X_PATH, xPath);
     }
@@ -1159,8 +1164,7 @@ private String getMimeDataType(String mimeType) {
     }
 
     private static String generateNextName(String name) {
-        Pattern pattern = Pattern.compile("\\d+\\z");
-        Matcher matcher = pattern.matcher(name);
+        Matcher matcher = TRAILING_DIGITS.matcher(name);
         if (matcher.find()) {
             String numStr = matcher.group();
             int num = Integer.parseInt(numStr) + 1;
@@ -1192,7 +1196,7 @@ public String toVarName(String name) {
 
     public String toVarName(String prefix, String name) {
         boolean hasPrefix = !StringUtils.isBlank(prefix);
-        name = underscore(sanitizeName(name.replaceAll("-", "_")));
+        name = underscore(sanitizeName(MINUS.matcher(name).replaceAll("_")));
         if (name.equals("_")) {
             name = "underscore";
         }
@@ -1201,7 +1205,7 @@ public String toVarName(String prefix, String name) {
         if (hasPrefix) {
             return prefix + name;
         } else {
-            if (name.matches("^\\d.*"))
+            if (STARTS_WITH_DIGIT.matcher(name).matches())
                 name = escapeReservedWord(name);
             if (isReservedWord(name))
                 name = escapeReservedWord(name);
@@ -1266,7 +1270,7 @@ public String escapeIdentifier(String prefix, String name) {
         if (isReservedWord(name)) {
             name = prefix + name;
         }
-        if (name.matches("^\\d.*")) {
+        if (STARTS_WITH_DIGIT.matcher(name).matches()) {
             name = prefix + name; // e.g. 200Response => Model200Response (after camelize)
         }
         if (languageSpecificPrimitives.contains(name)) {
@@ -1429,9 +1433,9 @@ public String toEnumVarName(String value, String datatype) {
         // number
         if (num.contains(datatype.toLowerCase(Locale.ROOT))) {
             String varName = "Num" + value;
-            varName = varName.replaceAll("-", "Minus_");
-            varName = varName.replaceAll("\\+", "Plus_");
-            varName = varName.replaceAll("\\.", "_Dot_");
+            varName = MINUS.matcher(varName).replaceAll("Minus_");
+            varName = PLUS.matcher(varName).replaceAll("Plus_");
+            varName = DOT.matcher(varName).replaceAll("_Dot_");
             return "'" + StringUtils.capitalize(sanitizeName(varName));
         }
 
@@ -1462,10 +1466,10 @@ public String escapeText(String input) {
         // outer unescape to retain the original multi-byte characters
         // finally escalate characters avoiding code injection
         return escapeUnsafeCharacters(
-                StringEscapeUtils.unescapeJava(
+                CONTROL_WHITESPACE.matcher(StringEscapeUtils.unescapeJava(
                                 StringEscapeUtils.escapeJava(input)
-                                        .replace("\\/", "/"))
-                        .replaceAll("[\\t\\n\\r]", " ")
+                                        .replace("\\/", "/")))
+                        .replaceAll(" ")
                         .replace("\\", "\\\\")
                         .replace("\"", "\\\""));
     }
diff --git a/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/HaskellServantCodegen.java b/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/HaskellServantCodegen.java
index 06703ff40856..383575bec51a 100644
--- a/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/HaskellServantCodegen.java
+++ b/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/HaskellServantCodegen.java
@@ -42,7 +42,6 @@ public class HaskellServantCodegen extends DefaultCodegen implements CodegenConf
     // source folder where to write the files
     protected String sourceFolder = "src";
     protected String apiVersion = "0.0.1";
-    private static final Pattern LEADING_UNDERSCORE = Pattern.compile("^_+");
 
     public static final String PROP_SERVE_STATIC = "serveStatic";
     public static final String PROP_SERVE_STATIC_DESC = "serve will serve files from the directory 'static'.";
@@ -598,7 +597,7 @@ public CodegenOperation fromOperation(String resourcePath, String httpMethod, Op
                 // Because headers is a Map multiple Set-Cookie headers are currently not possible. If someone
                 // uses the workaround with null bytes, remove them and add add each header to the list:
                 // https://github.com/OAI/OpenAPI-Specification/issues/1237#issuecomment-906603675
-                String headerName = h.baseName.replaceAll("\0", "");
+                String headerName = h.baseName.replace("\0", "");
                 String headerType = h.dataType;
                 headerContents.add("Header \"" + headerName + "\" " + headerType);
             }
@@ -609,7 +608,7 @@ public CodegenOperation fromOperation(String resourcePath, String httpMethod, Op
 
         String code = "200";
         for (CodegenResponse r : op.responses) {
-            if (r.code.matches("2[0-9][0-9]")) {
+            if (HTTP_2XX_CODE.matcher(r.code).matches()) {
                 code = r.code;
                 break;
             }
diff --git a/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/HaskellYesodServerCodegen.java b/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/HaskellYesodServerCodegen.java
index 38e1ba948657..5809707c5299 100644
--- a/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/HaskellYesodServerCodegen.java
+++ b/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/HaskellYesodServerCodegen.java
@@ -45,8 +45,6 @@ public class HaskellYesodServerCodegen extends DefaultCodegen implements Codegen
     public static final String PROJECT_NAME = "projectName";
     public static final String API_MODULE_NAME = "apiModuleName";
 
-    private static final Pattern LEADING_UNDERSCORE = Pattern.compile("^_+");
-
     private final Logger LOGGER = LoggerFactory.getLogger(HaskellYesodServerCodegen.class);
 
     @Getter @Setter
diff --git a/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/JMeterClientCodegen.java b/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/JMeterClientCodegen.java
index d005f54111b6..55c62a97823d 100644
--- a/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/JMeterClientCodegen.java
+++ b/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/JMeterClientCodegen.java
@@ -154,7 +154,7 @@ public void preprocessOpenAPI(OpenAPI openAPI) {
                 PathItem path = openAPIGetPathsEntry.getValue();
                 if (path.readOperations() != null) {
                     for (Operation operation : path.readOperations()) {
-                        String pathWithDollars = pathname.replaceAll("\\{", "\\$\\{");
+                        String pathWithDollars =  LEFT_CURLY_BRACE.matcher(pathname).replaceAll("\\${");
                         operation.addExtension("x-path", pathWithDollars);
                     }
                 }
diff --git a/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/JavaClientCodegen.java b/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/JavaClientCodegen.java
index b2faed874176..39e72aac1efb 100644
--- a/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/JavaClientCodegen.java
+++ b/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/JavaClientCodegen.java
@@ -59,6 +59,9 @@ public class JavaClientCodegen extends AbstractJavaCodegen
 
     private final Logger LOGGER = LoggerFactory.getLogger(JavaClientCodegen.class);
 
+    /** Matches a Feign-style custom HTTP method suffix, e.g. {@code /path:customMethod}. */
+    private static final Pattern FEIGN_CUSTOM_METHOD = Pattern.compile("^(.*):([^:]*)$");
+
     public static final String USE_RX_JAVA2 = "useRxJava2";
     public static final String USE_RX_JAVA3 = "useRxJava3";
     public static final String DO_NOT_USE_RX = "doNotUseRx";
@@ -942,13 +945,12 @@ public int compare(CodegenParameter one, CodegenParameter another) {
         if (isLibrary(FEIGN) || isLibrary(FEIGN_HC5)) {
             OperationMap operations = objs.getOperations();
             List<CodegenOperation> operationList = operations.getOperation();
-            Pattern methodPattern = Pattern.compile("^(.*):([^:]*)$");
             for (CodegenOperation op : operationList) {
                 String path = op.path;
                 String method = "";
 
                 // if a custom method is found at the end of the path, cut it off for later
-                Matcher m = methodPattern.matcher(path);
+                Matcher m = FEIGN_CUSTOM_METHOD.matcher(path);
                 if (m.find()) {
                     path = m.group(1);
                     method = m.group(2);
diff --git a/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/JavaDubboServerCodegen.java b/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/JavaDubboServerCodegen.java
index 5d28f7b0b554..8be3b7da5f9d 100644
--- a/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/JavaDubboServerCodegen.java
+++ b/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/JavaDubboServerCodegen.java
@@ -401,8 +401,7 @@ public void processOpts() {
 
             if (isUserTitle) {
                 String titleName = (String) additionalProperties.get(TITLE);
-                mainClassName = (camelize(titleName.trim(), CamelizeOption.UPPERCASE_FIRST_CHAR) + "Application").replaceAll("\\s+", "");
-                ;
+                mainClassName = WHITESPACE.matcher(camelize(titleName.trim(), CamelizeOption.UPPERCASE_FIRST_CHAR) + "Application").replaceAll("");
             } else {
                 mainClassName = "OpenApiGeneratorApplication";
             }
@@ -455,7 +454,7 @@ private boolean isDubbo33OrHigher(String version) {
 
         try {
             String cleanVersion = version.split("-")[0];
-            String[] parts = cleanVersion.split("\\.");
+            String[] parts = DOT.split(cleanVersion);
             if (parts.length >= 2) {
                 int major = Integer.parseInt(parts[0]);
                 int minor = Integer.parseInt(parts[1]);
diff --git a/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/JavaHelidonCommonCodegen.java b/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/JavaHelidonCommonCodegen.java
index 3ca11c46b991..98359063a074 100644
--- a/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/JavaHelidonCommonCodegen.java
+++ b/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/JavaHelidonCommonCodegen.java
@@ -62,6 +62,9 @@
 public abstract class JavaHelidonCommonCodegen extends AbstractJavaCodegen
         implements BeanValidationFeatures, PerformBeanValidationFeatures {
 
+    private static final Pattern STATUS_PATTERN = Pattern.compile(
+            "public static final Status (\\w+)\\s*=\\s*new\\s*Status\\((\\d+)", Pattern.MULTILINE);
+
     static final String HELIDON_MP = "mp";
     static final String HELIDON_SE = "se";
 
@@ -488,10 +491,8 @@ private HashMap<String, String> loadKnownHttpStatusMap() {
             if (is == null) {
                 throw new RuntimeException("Unable to locate /java-helidon/common/Status.java to discover known HTTP statuses");
             }
-            Pattern statusPattern = Pattern.compile("public static final Status (\\w+)\\s*=\\s*new\\s*Status\\((\\d+)",
-                    Pattern.MULTILINE);
             return new Scanner(is, StandardCharsets.UTF_8)
-                    .findAll(statusPattern)
+                    .findAll(STATUS_PATTERN)
                     .collect(HashMap::new,
                             (map, match) -> map.put(match.group(2), match.group(1)),
                             Map::putAll);
@@ -937,10 +938,10 @@ private static List<String> localDefaultVersions() throws IOException {
             return Files.readAllLines(versionsFile.toPath());
         }
 
-        private static List<String> extractVersions(String xmlContent) {
-            Pattern versionPattern = Pattern.compile("<version[^>]*>([^>]+)</version>");
+        private static final Pattern VERSION_PATTERN = Pattern.compile("<version[^>]*>([^>]+)</version>");
 
-            Matcher matcher = versionPattern.matcher(xmlContent);
+        private static List<String> extractVersions(String xmlContent) {
+            Matcher matcher = VERSION_PATTERN.matcher(xmlContent);
             List<String> result = new ArrayList<>();
             while (matcher.find()) {
                 result.add(matcher.group(1));
diff --git a/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/JavaInflectorServerCodegen.java b/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/JavaInflectorServerCodegen.java
index ae73860f8c2a..7bea84bcc4f2 100644
--- a/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/JavaInflectorServerCodegen.java
+++ b/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/JavaInflectorServerCodegen.java
@@ -238,7 +238,7 @@ public String toApiName(String name) {
         if (name.length() == 0) {
             return "DefaultController";
         }
-        name = name.replaceAll("[^a-zA-Z0-9]+", "_");
+        name = NON_ALPHANUMERIC.matcher(name).replaceAll("_");
         return camelize(name) + "Controller";
     }
 }
diff --git a/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/JavaMicronautAbstractCodegen.java b/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/JavaMicronautAbstractCodegen.java
index 0ff8db956a42..069ed20ca45a 100644
--- a/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/JavaMicronautAbstractCodegen.java
+++ b/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/JavaMicronautAbstractCodegen.java
@@ -403,17 +403,17 @@ public void processOpts() {
     @Override
     public String apiTestFileFolder() {
         if (testTool.equals(OPT_TEST_SPOCK)) {
-            return getOutputDir() + "/src/test/groovy/" + apiPackage().replaceAll("\\.", "/");
+            return getOutputDir() + "/src/test/groovy/" + DOT.matcher(apiPackage()).replaceAll("/");
         }
-        return getOutputDir() + "/src/test/java/" + apiPackage().replaceAll("\\.", "/");
+        return getOutputDir() + "/src/test/java/" + DOT.matcher(apiPackage()).replaceAll("/");
     }
 
     @Override
     public String modelTestFileFolder() {
         if (testTool.equals(OPT_TEST_SPOCK)) {
-            return getOutputDir() + "/src/test/groovy/" + modelPackage().replaceAll("\\.", "/");
+            return getOutputDir() + "/src/test/groovy/" + DOT.matcher(modelPackage()).replaceAll("/");
         }
-        return getOutputDir() + "/src/test/java/" + modelPackage().replaceAll("\\.", "/");
+        return getOutputDir() + "/src/test/java/" + DOT.matcher(modelPackage()).replaceAll("/");
     }
 
     @Override
@@ -694,6 +694,7 @@ public String escapeTextGroovy(String text) {
         if (text == null) {
             return null;
         }
+        //TODO: this seems like a bug, since it is basically no-op currently. Probably .replace instead of .replaceAll is wanted here?
         return escapeText(text).replaceAll("'", "\\'");
     }
 
diff --git a/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/JavaPlayFrameworkCodegen.java b/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/JavaPlayFrameworkCodegen.java
index 9f2743be01de..86b227ca17f6 100644
--- a/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/JavaPlayFrameworkCodegen.java
+++ b/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/JavaPlayFrameworkCodegen.java
@@ -33,13 +33,13 @@
 import java.io.File;
 import java.util.*;
 import java.util.regex.Matcher;
-import java.util.regex.Pattern;
 
 import static org.openapitools.codegen.utils.CamelizeOption.LOWERCASE_FIRST_LETTER;
 import static org.openapitools.codegen.utils.StringUtils.camelize;
 
 public class JavaPlayFrameworkCodegen extends AbstractJavaCodegen implements BeanValidationFeatures {
     private final Logger LOGGER = LoggerFactory.getLogger(JavaPlayFrameworkCodegen.class);
+
     public static final String TITLE = "title";
     public static final String CONFIG_PACKAGE = "configPackage";
     public static final String BASE_PACKAGE = "basePackage";
@@ -245,8 +245,7 @@ public OperationsMap postProcessOperationsWithModels(OperationsMap objs, List<Mo
                     }
                 }
 
-                Pattern pathVariableMatcher = Pattern.compile("\\{([^}]+)}");
-                Matcher match = pathVariableMatcher.matcher(operation.path);
+                Matcher match = PATH_PARAMETER.matcher(operation.path);
                 while (match.find()) {
                     String completeMatch = match.group();
                     String replacement = ":" + camelize(match.group(1), LOWERCASE_FIRST_LETTER);
diff --git a/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/JavaUndertowServerCodegen.java b/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/JavaUndertowServerCodegen.java
index 5437e15f9b59..8d5a39b3d8e8 100644
--- a/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/JavaUndertowServerCodegen.java
+++ b/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/JavaUndertowServerCodegen.java
@@ -215,7 +215,7 @@ public String toApiName(String name) {
         if (name.length() == 0) {
             return "DefaultHandler";
         }
-        name = name.replaceAll("[^a-zA-Z0-9]+", "_"); // FIXME: a parameter should not be assigned. Also declare the methods parameters as 'final'.
+        name = NON_ALPHANUMERIC.matcher(name).replaceAll("_"); // FIXME: a parameter should not be assigned. Also declare the methods parameters as 'final'.
         return camelize(name) + "Handler";
     }
 }
diff --git a/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/JavaVertXServerCodegen.java b/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/JavaVertXServerCodegen.java
index a06e46ffb675..30e2964e10d5 100644
--- a/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/JavaVertXServerCodegen.java
+++ b/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/JavaVertXServerCodegen.java
@@ -46,6 +46,9 @@
 public class JavaVertXServerCodegen extends AbstractJavaCodegen {
     private final Logger LOGGER = LoggerFactory.getLogger(JavaVertXServerCodegen.class);
 
+    private static final Pattern PATH_VARIABLE_PATTERN = Pattern.compile("\\{([^/]*)\\}");
+    private static final Pattern UNDERSCORE_CAPITALIZE_PATTERN = Pattern.compile("(_)(.)");
+
     protected String resourceFolder = "src/main/resources";
     protected String rootPackage = "org.openapitools.server.api";
     protected String apiVersion = "1.0.0-SNAPSHOT";
@@ -287,7 +290,7 @@ private String computeServiceId(String pathname, Entry<HttpMethod, Operation> en
         String operationId = entry.getValue().getOperationId();
         return (operationId != null) ? operationId
                 : entry.getKey().name()
-                + pathname.replaceAll("-", "_").replaceAll("/", "_").replaceAll("[{}]", "");
+                + MINUS.matcher(pathname).replaceAll("_").replaceAll("/", "_").replaceAll("[{}]", "");
     }
 
     protected String extractPortFromHost(String host) {
@@ -302,17 +305,15 @@ protected String extractPortFromHost(String host) {
 
     private String camelizePath(String path) {
         String word = path;
-        Pattern pattern = Pattern.compile("\\{([^/]*)\\}");
-        Matcher matcher = pattern.matcher(word);
+        Matcher matcher = PATH_VARIABLE_PATTERN.matcher(word);
         while (matcher.find()) {
             word = matcher.replaceFirst(":" + matcher.group(1));
-            matcher = pattern.matcher(word);
+            matcher = PATH_VARIABLE_PATTERN.matcher(word);
         }
-        pattern = Pattern.compile("(_)(.)");
-        matcher = pattern.matcher(word);
+        matcher = UNDERSCORE_CAPITALIZE_PATTERN.matcher(word);
         while (matcher.find()) {
             word = matcher.replaceFirst(matcher.group(2).toUpperCase(Locale.ROOT));
-            matcher = pattern.matcher(word);
+            matcher = UNDERSCORE_CAPITALIZE_PATTERN.matcher(word);
         }
         return word;
     }
diff --git a/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/JavascriptApolloClientCodegen.java b/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/JavascriptApolloClientCodegen.java
index 03fe2bf5ba88..118984fab16e 100644
--- a/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/JavascriptApolloClientCodegen.java
+++ b/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/JavascriptApolloClientCodegen.java
@@ -48,6 +48,10 @@ public class JavascriptApolloClientCodegen extends DefaultCodegen implements Cod
     @SuppressWarnings("hiding")
     private final Logger LOGGER = LoggerFactory.getLogger(JavascriptApolloClientCodegen.class);
 
+    /** Matches JS/JsDoc primitive type names for quoting in documentation. */
+    private static final java.util.regex.Pattern JS_PRIMITIVE_TYPES =
+            java.util.regex.Pattern.compile("\\b(Boolean|Integer|Number|String|Date|Blob)\\b");
+
     public static final String PROJECT_NAME = "projectName";
     public static final String MODULE_NAME = "moduleName";
     public static final String PROJECT_DESCRIPTION = "projectDescription";
@@ -482,7 +486,7 @@ public String toVarName(String name) {
         }
 
         // if it's all upper case, do nothing
-        if (name.matches("^[A-Z_]*$")) {
+        if (ALL_UPPER_UNDERSCORE.matcher(name).matches()) {
             return name;
         }
 
@@ -491,7 +495,7 @@ public String toVarName(String name) {
         name = getNameUsingModelPropertyNaming(name);
 
         // for reserved word or word starting with number, append _
-        if (isReservedWord(name) || name.matches("^\\d.*")) {
+        if (isReservedWord(name) || STARTS_WITH_DIGIT.matcher(name).matches()) {
             name = escapeReservedWord(name);
         }
 
@@ -533,7 +537,7 @@ public String toModelName(String name) {
         }
 
         // model name starts with number
-        if (name.matches("^\\d.*")) {
+        if (STARTS_WITH_DIGIT.matcher(name).matches()) {
             String modelName = "Model" + name; // e.g. 200Response => Model200Response (after camelize)
             LOGGER.warn("{} (model name starts with number) cannot be used as model name. Renamed to {}", name,
                     modelName);
@@ -782,7 +786,7 @@ protected String setPropertyExampleValue(CodegenProperty p) {
      * @return Normalized type
      */
     private String normalizeType(String type) {
-        return type.replaceAll("\\b(Boolean|Integer|Number|String|Date|Blob)\\b", "'$1'");
+        return JS_PRIMITIVE_TYPES.matcher(type).replaceAll("'$1'");
     }
 
     @Override
@@ -820,7 +824,7 @@ public String toOperationId(String operationId) {
         }
 
         // operationId starts with a number
-        if (operationId.matches("^\\d.*")) {
+        if (STARTS_WITH_DIGIT.matcher(operationId).matches()) {
             String newOperationId = camelize("call_" + operationId, LOWERCASE_FIRST_LETTER);
             LOGGER.warn("{} (starting with a number) cannot be used as method name. Renamed to {}", operationId, newOperationId);
             return newOperationId;
diff --git a/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/JavascriptClientCodegen.java b/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/JavascriptClientCodegen.java
index 83c7550546f8..f44aabdb513e 100644
--- a/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/JavascriptClientCodegen.java
+++ b/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/JavascriptClientCodegen.java
@@ -97,6 +97,10 @@ public class JavascriptClientCodegen extends DefaultCodegen implements CodegenCo
     @Setter
     protected boolean useURLSearchParams = true;
 
+    /** Matches JS/JsDoc primitive type names for quoting in documentation. */
+    private static final java.util.regex.Pattern JS_PRIMITIVE_TYPES =
+            java.util.regex.Pattern.compile("\\b(Boolean|Integer|Number|String|Date|Blob)\\b");
+
     public JavascriptClientCodegen() {
         super();
 
@@ -499,7 +503,7 @@ public String toVarName(String name) {
         }
 
         // if it's all upper case, do nothing
-        if (name.matches("^[A-Z_]*$")) {
+        if (ALL_UPPER_UNDERSCORE.matcher(name).matches()) {
             return name;
         }
 
@@ -508,7 +512,7 @@ public String toVarName(String name) {
         name = getNameUsingModelPropertyNaming(name);
 
         // for reserved word or word starting with number, append _
-        if (isReservedWord(name) || name.matches("^\\d.*")) {
+        if (isReservedWord(name) || STARTS_WITH_DIGIT.matcher(name).matches()) {
             name = escapeReservedWord(name);
         }
 
@@ -560,7 +564,7 @@ public String toModelName(String name) {
         }
 
         // model name starts with number
-        if (name.matches("^\\d.*")) {
+        if (STARTS_WITH_DIGIT.matcher(name).matches()) {
             String modelName = "Model" + name; // e.g. 200Response => Model200Response (after camelize)
             LOGGER.warn("{} (model name starts with number) cannot be used as model name. Renamed to {}", name,
                     modelName);
@@ -809,7 +813,7 @@ protected String setPropertyExampleValue(CodegenProperty p) {
      * @return Normalized type
      */
     private String normalizeType(String type) {
-        return type.replaceAll("\\b(Boolean|Integer|Number|String|Date|Blob)\\b", "'$1'");
+        return JS_PRIMITIVE_TYPES.matcher(type).replaceAll("'$1'");
     }
 
     @Override
@@ -847,7 +851,7 @@ public String toOperationId(String operationId) {
         }
 
         // operationId starts with a number
-        if (operationId.matches("^\\d.*")) {
+        if (STARTS_WITH_DIGIT.matcher(operationId).matches()) {
             String newOperationId = camelize("call_" + operationId, LOWERCASE_FIRST_LETTER);
             LOGGER.warn("{} (starting with a number) cannot be used as method name. Renamed to {}", operationId, newOperationId);
             return newOperationId;
diff --git a/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/JavascriptClosureAngularClientCodegen.java b/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/JavascriptClosureAngularClientCodegen.java
index 3629b1ed4d19..43563ffdc421 100644
--- a/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/JavascriptClosureAngularClientCodegen.java
+++ b/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/JavascriptClosureAngularClientCodegen.java
@@ -186,10 +186,10 @@ public String toVarName(String name) {
         name = sanitizeName(name);
 
         // replace - with _ e.g. created-at => created_at
-        name = name.replaceAll("-", "_");
+        name = MINUS.matcher(name).replaceAll("_");
 
         // if it's all upper case, do nothing
-        if (name.matches("^[A-Z_]*$"))
+        if (ALL_UPPER_UNDERSCORE.matcher(name).matches())
             return name;
 
         // camelize the variable name
@@ -197,7 +197,7 @@ public String toVarName(String name) {
         name = camelize(name, LOWERCASE_FIRST_LETTER);
 
         // for reserved word or word starting with number, append _
-        if (isReservedWord(name) || name.matches("^\\d.*"))
+        if (isReservedWord(name) || STARTS_WITH_DIGIT.matcher(name).matches())
             name = escapeReservedWord(name);
 
         return name;
diff --git a/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/JetbrainsHttpClientClientCodegen.java b/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/JetbrainsHttpClientClientCodegen.java
index 5f6711b6d39a..9caedfb94c69 100644
--- a/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/JetbrainsHttpClientClientCodegen.java
+++ b/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/JetbrainsHttpClientClientCodegen.java
@@ -147,9 +147,7 @@ public static class DoubleMustacheLambda implements Mustache.Lambda {
         @Override
         public void execute(Template.Fragment fragment, Writer writer) throws IOException {
             String text = fragment.execute();
-            writer.write(text
-                    .replaceAll("\\{", "{{")
-                    .replaceAll("}", "}}")
+            writer.write(RIGHT_CURLY_BRACE.matcher(LEFT_CURLY_BRACE.matcher(text).replaceAll("{{")).replaceAll("}}")
             );
         }
     }
diff --git a/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/K6ClientCodegen.java b/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/K6ClientCodegen.java
index 0206116364d7..61577427735e 100644
--- a/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/K6ClientCodegen.java
+++ b/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/K6ClientCodegen.java
@@ -778,7 +778,7 @@ public String toVarName(String name) {
         }
 
         // if it's all upper case, do nothing
-        if (name.matches("^[A-Z_]*$")) {
+        if (ALL_UPPER_UNDERSCORE.matcher(name).matches()) {
             return name;
         }
 
@@ -787,7 +787,7 @@ public String toVarName(String name) {
         name = getNameUsingModelPropertyNaming(name);
 
         // for reserved word or word starting with number, append _
-        if (isReservedWord(name) || name.matches("^\\d.*")) {
+        if (isReservedWord(name) || STARTS_WITH_DIGIT.matcher(name).matches()) {
             name = escapeReservedWord(name);
         }
 
diff --git a/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/KotlinSpringServerCodegen.java b/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/KotlinSpringServerCodegen.java
index 6730dd636649..053256cd2112 100644
--- a/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/KotlinSpringServerCodegen.java
+++ b/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/KotlinSpringServerCodegen.java
@@ -56,6 +56,10 @@ public class KotlinSpringServerCodegen extends AbstractKotlinCodegen
     private final Logger LOGGER =
             LoggerFactory.getLogger(KotlinSpringServerCodegen.class);
 
+    /** Matches {@code kotlin.collections.Mutable} prefix — replaced with its immutable counterpart. */
+    private static final java.util.regex.Pattern KOTLIN_MUTABLE_COLLECTION =
+            java.util.regex.Pattern.compile("kotlin\\.collections\\.Mutable");
+
     private static final HashSet<String> VARIABLE_RESERVED_WORDS =
             new HashSet<>(Arrays.asList(
                     "ApiClient",
@@ -1363,7 +1367,7 @@ public Map<String, Object> postProcessSupportingFileData(Map<String, Object> obj
 
     private String getNonMutableContainerTypeIfNeeded(String type) {
         if (type != null && type.contains("kotlin.collections.Mutable")) {
-            return type.replaceAll("kotlin\\.collections\\.Mutable", "kotlin.collections.");
+            return KOTLIN_MUTABLE_COLLECTION.matcher(type).replaceAll("kotlin.collections.");
         }
         return type;
     }
diff --git a/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/KtormSchemaCodegen.java b/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/KtormSchemaCodegen.java
index 4483eec5daee..6113f049f306 100644
--- a/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/KtormSchemaCodegen.java
+++ b/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/KtormSchemaCodegen.java
@@ -44,6 +44,8 @@
 public class KtormSchemaCodegen extends AbstractKotlinCodegen {
     private final Logger LOGGER = LoggerFactory.getLogger(KtormSchemaCodegen.class);
 
+    private static final Pattern UNSAFE_IDENTIFIER_CHARS = Pattern.compile("[^0-9a-zA-Z$_\\u0080-\\uFFFF]");
+
     public static final String VENDOR_EXTENSION_SCHEMA = "x-ktorm-schema";
     public static final String DEFAULT_DATABASE_NAME = "defaultDatabaseName";
     public static final String IMPORT_MODEL_PACKAGE_NAME = "importModelPackageName";
@@ -1061,13 +1063,13 @@ public String toColumnName(String name) {
     public String toIdentifier(String name, String prefix, String suffix) {
         String escapedName = escapeQuotedIdentifier(name);
         // Database, table, and column names cannot end with space characters.
-        if (escapedName.matches(".*\\s$")) {
+        if (ENDS_WITH_WHITESPACE.matcher(escapedName).matches()) {
             LOGGER.warn("Database, table, and column names cannot end with space characters. Check '{}' name", name);
-            escapedName = escapedName.replaceAll("\\s+$", "");
+            escapedName = TRAILING_WHITESPACE.matcher(escapedName).replaceAll("");
         }
 
         // Identifiers may begin with a digit but unless quoted may not consist solely of digits.
-        if (escapedName.matches("^\\d+$")) {
+        if (DIGITS_ONLY.matcher(escapedName).matches()) {
             LOGGER.warn("Database, table, and column names cannot consist solely of digits. Check '{}' name", name);
             escapedName = prefix + escapedName + suffix;
         }
@@ -1091,12 +1093,11 @@ public String escapeQuotedIdentifier(String identifier) {
         // ASCII: [0-9,a-z,A-Z$_] (basic Latin letters, digits 0-9, dollar, underscore) Extended: U+0080 .. U+FFFF
         // ASCII NUL (U+0000) and supplementary characters (U+10000 and higher) are not permitted in quoted or unquoted identifiers.
         // This does in fact matches against >\xFFFF and against ^\x0000. works only on Java7+
-        Pattern regexp = Pattern.compile("[^0-9a-zA-z$_\\x0080-\\xFFFF]");
-        Matcher matcher = regexp.matcher(identifier);
+        Matcher matcher = UNSAFE_IDENTIFIER_CHARS.matcher(identifier);
         if (matcher.find()) {
             LOGGER.warn("Identifier '{}' contains unsafe characters out of [0-9,a-z,A-Z$_] and U+0080..U+FFFF range",
                     identifier);
-            identifier = identifier.replaceAll("[^0-9a-zA-z$_\\x0080-\\xFFFF]", "");
+            identifier = matcher.reset().replaceAll("");
         }
         return identifier;
     }
@@ -1166,7 +1167,7 @@ public String toSrcPath(String packageName) {
         // Trim prefix file separators from package path
         String packagePath = StringUtils.removeStart(
                 // Replace period, backslash, forward slash with file separator in package name
-                packageName.replaceAll("[\\.\\\\/]", Matcher.quoteReplacement("/")),
+                PACKAGE_SEPARATOR.matcher(packageName).replaceAll(Matcher.quoteReplacement("/")),
                 File.separator
         );
 
diff --git a/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/LuaClientCodegen.java b/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/LuaClientCodegen.java
index 92c38a91f562..4232dbbfcd42 100644
--- a/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/LuaClientCodegen.java
+++ b/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/LuaClientCodegen.java
@@ -249,10 +249,11 @@ public String toVarName(String name) {
         }
 
         // replace - with _ e.g. created-at => created_at
-        name = sanitizeName(name.replaceAll("-", "_"));
+        name = sanitizeName(MINUS.matcher(name).replaceAll("_"));
+        name = sanitizeName(MINUS.matcher(name).replaceAll("_"));
 
         // if it's all upper case, do nothing
-        if (name.matches("^[A-Z_]*$"))
+        if (ALL_UPPER_UNDERSCORE.matcher(name).matches())
             return name;
 
         // convert variable name to snake case
@@ -264,7 +265,7 @@ public String toVarName(String name) {
             name = escapeReservedWord(name);
 
         // for reserved word or word starting with number, append _
-        if (name.matches("^\\d.*"))
+        if (STARTS_WITH_DIGIT.matcher(name).matches())
             name = "Var" + name;
 
         return name;
@@ -309,7 +310,7 @@ public String toModelFilename(String name) {
         }
 
         // model name starts with number
-        if (name.matches("^\\d.*")) {
+        if (STARTS_WITH_DIGIT.matcher(name).matches()) {
             LOGGER.warn("{} (model name starts with number) cannot be used as model name. Renamed to {}", name,
                     "model_" + name);
             name = "model_" + name; // e.g. 200Response => Model200Response (after camelize)
@@ -321,7 +322,7 @@ public String toModelFilename(String name) {
     @Override
     public String toApiFilename(String name) {
         // replace - with _ e.g. created-at => created_at
-        name = name.replaceAll("-", "_"); // FIXME: a parameter should not be assigned. Also declare the methods parameters as 'final'.
+        name = MINUS.matcher(name).replaceAll("_"); // FIXME: a parameter should not be assigned. Also declare the methods parameters as 'final'.
 
         // e.g. PetApi.lua => pet_api.lua
         return underscore(name) + "_api";
@@ -545,9 +546,9 @@ public String toEnumVarName(String name, String datatype) {
         // number
         if ("int".equals(datatype) || "double".equals(datatype) || "float".equals(datatype)) {
             String varName = name;
-            varName = varName.replaceAll("-", "MINUS_");
-            varName = varName.replaceAll("\\+", "PLUS_");
-            varName = varName.replaceAll("\\.", "_DOT_");
+            varName = MINUS.matcher(varName).replaceAll("MINUS_");
+            varName = PLUS.matcher(varName).replaceAll("PLUS_");
+            varName = DOT.matcher(varName).replaceAll("_DOT_");
             return varName;
         }
 
@@ -558,10 +559,10 @@ public String toEnumVarName(String name, String datatype) {
 
         // string
         String enumName = sanitizeName(underscore(name).toUpperCase(Locale.ROOT));
-        enumName = enumName.replaceFirst("^_", "");
-        enumName = enumName.replaceFirst("_$", "");
+        enumName = FIRST_LEADING_UNDERSCORE.matcher(enumName).replaceFirst("");
+        enumName = LAST_TRAILING_UNDERSCORE.matcher(enumName).replaceFirst("");
 
-        if (isReservedWord(enumName) || enumName.matches("\\d.*")) { // reserved word or starts with number
+        if (isReservedWord(enumName) || STARTS_WITH_DIGIT.matcher(enumName).matches()) { // reserved word or starts with number
             return escapeReservedWord(enumName);
         } else {
             return enumName;
@@ -575,7 +576,7 @@ public String toEnumName(CodegenProperty property) {
         // remove [] for array or map of enum
         enumName = enumName.replace("[]", "");
 
-        if (enumName.matches("\\d.*")) { // starts with number
+        if (STARTS_WITH_DIGIT.matcher(enumName).matches()) { // starts with number
             return "_" + enumName;
         } else {
             return enumName;
diff --git a/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/MysqlSchemaCodegen.java b/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/MysqlSchemaCodegen.java
index 1da17d653d06..ecb67b92bfc3 100644
--- a/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/MysqlSchemaCodegen.java
+++ b/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/MysqlSchemaCodegen.java
@@ -37,6 +37,11 @@
 public class MysqlSchemaCodegen extends DefaultCodegen implements CodegenConfig {
     private final Logger LOGGER = LoggerFactory.getLogger(MysqlSchemaCodegen.class);
 
+    /** Unsafe characters for unquoted MySQL identifiers: outside [0-9,a-z,A-Z,$,_,U+0080..U+FFFF]. */
+    private static final Pattern UNSAFE_UNQUOTED_IDENTIFIER_CHARS = Pattern.compile("[^0-9a-zA-Z$_\\u0080-\\uFFFF]");
+    /** Unsafe characters for quoted MySQL identifiers: outside [U+0001..U+007F, U+0080..U+FFFF]. */
+    private static final Pattern UNSAFE_QUOTED_IDENTIFIER_CHARS = Pattern.compile("[^\\u0001-\\u007F\\u0080-\\uFFFF]");
+
     public static final String VENDOR_EXTENSION_MYSQL_SCHEMA = "x-mysql-schema";
     public static final String DEFAULT_DATABASE_NAME = "defaultDatabaseName";
     public static final String JSON_DATA_TYPE_ENABLED = "jsonDataTypeEnabled";
@@ -1081,13 +1086,13 @@ public String toColumnName(String name) {
     public String toMysqlIdentifier(String name, String prefix, String suffix) {
         String escapedName = escapeMysqlQuotedIdentifier(name);
         // Database, table, and column names cannot end with space characters.
-        if (escapedName.matches(".*\\s$")) {
+        if (ENDS_WITH_WHITESPACE.matcher(escapedName).matches()) {
             LOGGER.warn("Database, table, and column names cannot end with space characters. Check '{}' name", name);
-            escapedName = escapedName.replaceAll("\\s+$", "");
+            escapedName = TRAILING_WHITESPACE.matcher(escapedName).replaceAll("");
         }
 
         // Identifiers may begin with a digit but unless quoted may not consist solely of digits.
-        if (escapedName.matches("^\\d+$")) {
+        if (DIGITS_ONLY.matcher(escapedName).matches()) {
             LOGGER.warn("Database, table, and column names cannot consist solely of digits. Check '{}' name", name);
             escapedName = prefix + escapedName + suffix;
         }
@@ -1108,12 +1113,11 @@ public String toMysqlIdentifier(String name, String prefix, String suffix) {
      */
     public String escapeMysqlUnquotedIdentifier(String identifier) {
         // ASCII: [0-9,a-z,A-Z$_] (basic Latin letters, digits 0-9, dollar, underscore) Extended: U+0080 .. U+FFFF
-        Pattern regexp = Pattern.compile("[^0-9a-zA-z$_\\u0080-\\uFFFF]");
-        Matcher matcher = regexp.matcher(identifier);
+        Matcher matcher = UNSAFE_UNQUOTED_IDENTIFIER_CHARS.matcher(identifier);
         if (matcher.find()) {
             LOGGER.warn("Identifier '{}' contains unsafe characters out of [0-9,a-z,A-Z$_] and U+0080..U+FFFF range",
                     identifier);
-            identifier = identifier.replaceAll("[^0-9a-zA-z$_\\u0080-\\uFFFF]", "");
+            identifier = matcher.reset().replaceAll("");
         }
 
         // ASCII NUL (U+0000) and supplementary characters (U+10000 and higher) are not permitted in quoted or unquoted identifiers.
@@ -1131,12 +1135,11 @@ public String escapeMysqlUnquotedIdentifier(String identifier) {
      */
     public String escapeMysqlQuotedIdentifier(String identifier) {
         // ASCII: U+0001 .. U+007F Extended: U+0080 .. U+FFFF
-        Pattern regexp = Pattern.compile("[^\\u0001-\\u007F\\u0080-\\uFFFF]");
-        Matcher matcher = regexp.matcher(identifier);
+        Matcher matcher = UNSAFE_QUOTED_IDENTIFIER_CHARS.matcher(identifier);
         if (matcher.find()) {
             LOGGER.warn("Identifier '{}' contains unsafe characters out of U+0001..U+007F and U+0080..U+FFFF range",
                     identifier);
-            identifier = identifier.replaceAll("[^\\u0001-\\u007F\\u0080-\\uFFFF]", "");
+            identifier = matcher.reset().replaceAll("");
         }
 
         // ASCII NUL (U+0000) and supplementary characters (U+10000 and higher) are not permitted in quoted or unquoted identifiers.
@@ -1208,7 +1211,7 @@ public String toSrcPath(String packageName) {
         // Trim prefix file separators from package path
         String packagePath = StringUtils.removeStart(
                 // Replace period, backslash, forward slash with file separator in package name
-                packageName.replaceAll("[\\.\\\\/]", Matcher.quoteReplacement("/")),
+                PACKAGE_SEPARATOR.matcher(packageName).replaceAll(Matcher.quoteReplacement("/")),
                 File.separator
         );
 
diff --git a/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/N4jsClientCodegen.java b/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/N4jsClientCodegen.java
index 2448f1dc7e00..dc23d5c61f47 100644
--- a/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/N4jsClientCodegen.java
+++ b/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/N4jsClientCodegen.java
@@ -35,6 +35,7 @@
 
 import java.io.File;
 import java.util.*;
+import java.util.regex.Pattern;
 import java.util.stream.Collectors;
 
 import static org.openapitools.codegen.CodegenConstants.*;
@@ -43,7 +44,7 @@ public class N4jsClientCodegen extends DefaultCodegen implements CodegenConfig {
     public static final String CHECK_REQUIRED_PARAMS_NOT_NULL = "checkRequiredParamsNotNull";
     public static final String CHECK_SUPERFLUOUS_BODY_PROPS = "checkSuperfluousBodyProps";
     public static final String GENERATE_DEFAULT_API_EXECUTER = "generateDefaultApiExecuter";
-
+    private static final Pattern COMPOSED_TYPE_DELIMITERS = Pattern.compile("[|&<>]");
     final Logger LOGGER = LoggerFactory.getLogger(N4jsClientCodegen.class);
 
     final Set<String> forbiddenChars = new HashSet<>();
@@ -300,7 +301,7 @@ protected void addImport(Set<String> importsToBeAddedTo, String type) {
     }
 
     private String[] splitComposedType(String name) {
-        return name.replace(" ", "").split("[|&<>]");
+        return COMPOSED_TYPE_DELIMITERS.split(name.replace(" ", ""));
     }
 
     @Override
diff --git a/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/NimClientCodegen.java b/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/NimClientCodegen.java
index 35f3ff81c2d6..30bddfe35d1f 100644
--- a/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/NimClientCodegen.java
+++ b/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/NimClientCodegen.java
@@ -45,6 +45,14 @@ public class NimClientCodegen extends DefaultCodegen implements CodegenConfig {
 
     public static final String PROJECT_NAME = "projectName";
 
+    /** Matches an underscore, one or more digits, and a trailing underscore; used to strip version markers. */
+    private static final Pattern UNDERSCORE_DIGITS_UNDERSCORE = Pattern.compile("_(\\d+)_");
+    /** Matches an underscore followed by one or more digits at the end of a string. */
+    private static final Pattern UNDERSCORE_DIGITS_END = Pattern.compile("_(\\d+)$");
+    /** Matches a valid Nim type name: starts with an uppercase letter and continues with CamelCase segments. */
+    private static final Pattern NIM_TYPE_NAME = Pattern.compile(
+            "^(?:[A-Z]|[a-z]|[\\x80-\\xff])(_?(?:[A-Z]|[a-z]|[\\x80-\\xff]|[0-9]))*$");
+
     @Setter protected String packageName = "openapiclient";
     @Setter protected String packageVersion = "1.0.0";
 
@@ -416,7 +424,7 @@ public String escapeUnsafeCharacters(String input) {
     @Override
     public String toModelImport(String name) {
         name = normalizeSchemaName(name);
-        name = name.replaceAll("-", "_");
+        name = MINUS.matcher(name).replaceAll("_");
 
         if (importMapping.containsKey(name)) {
             return sanitizeNimIdentifier("model_" + StringUtils.underscore(importMapping.get(name)));
@@ -427,7 +435,7 @@ public String toModelImport(String name) {
 
     @Override
     public String toApiImport(String name) {
-        name = name.replaceAll("-", "_");
+        name = MINUS.matcher(name).replaceAll("_");
         if (importMapping.containsKey(name)) {
             return sanitizeNimIdentifier("api_" + StringUtils.underscore(importMapping.get(name)));
         } else {
@@ -443,12 +451,8 @@ private String normalizeSchemaName(String name) {
         if (name == null) {
             return null;
         }
-        // Remove underscores around and before digits (HTTP status codes, version numbers, etc.)
-        // e.g., "GetComments_200_response" -> "GetComments200response"
-        // e.g., "Config_anyOf_1" -> "ConfiganyOf1"
-        // This ensures consistent handling whether the name comes with or without underscores
-        name = name.replaceAll("_(\\d+)_", "$1");  // Underscores on both sides
-        name = name.replaceAll("_(\\d+)$", "$1");   // Trailing underscore before digits
+        name = UNDERSCORE_DIGITS_UNDERSCORE.matcher(name).replaceAll("$1");  // Underscores on both sides
+        name = UNDERSCORE_DIGITS_END.matcher(name).replaceAll("$1");   // Trailing underscore before digits
         return name;
     }
 
@@ -505,8 +509,8 @@ private void processComposedSchemaVariants(CodegenModel mdl, List<CodegenPropert
             // Sanitize baseName to remove underscores and properly format for Nim
             if (newVariant.baseName != null) {
                 // Remove trailing underscores and convert to proper format
-                String sanitizedBase = newVariant.baseName.replaceAll("_+$", ""); // Remove trailing underscores
-                if (sanitizedBase.length() > 0 && Character.isUpperCase(sanitizedBase.charAt(0))) {
+                String sanitizedBase = MULTI_TRAILING_UNDERSCORES.matcher(newVariant.baseName).replaceAll(""); // Remove trailing underscores
+                if (!sanitizedBase.isEmpty() && Character.isUpperCase(sanitizedBase.charAt(0))) {
                     newVariant.baseName = toModelName(sanitizedBase);
                 } else {
                     newVariant.baseName = sanitizeNimIdentifier(sanitizedBase);
@@ -517,7 +521,7 @@ private void processComposedSchemaVariants(CodegenModel mdl, List<CodegenPropert
             // For model types (not primitives), use toModelName to get the proper type name
             if (newVariant.dataType != null) {
                 // Check if this is a model type (starts with uppercase) vs primitive
-                if (newVariant.dataType.length() > 0 && Character.isUpperCase(newVariant.dataType.charAt(0))) {
+                if (!newVariant.dataType.isEmpty() && Character.isUpperCase(newVariant.dataType.charAt(0))) {
                     // This is likely a model type, use toModelName to properly format it
                     newVariant.dataType = toModelName(newVariant.dataType);
                 } else {
@@ -571,13 +575,13 @@ public String toModelName(String name) {
     @Override
     public String toModelFilename(String name) {
         name = normalizeSchemaName(name);
-        name = name.replaceAll("-", "_");
+        name = MINUS.matcher(name).replaceAll("_");
         return sanitizeNimIdentifier("model_" + StringUtils.underscore(name));
     }
 
     @Override
     public String toApiFilename(String name) {
-        name = name.replaceAll("-", "_");
+        name = MINUS.matcher(name).replaceAll("_");
         return sanitizeNimIdentifier("api_" + StringUtils.underscore(name));
     }
 
@@ -646,7 +650,7 @@ public String getTypeDeclaration(Schema p) {
             return typeMapping.get(schemaType);
         }
 
-        if (schemaType.matches("\\d.*")) { // starts with number
+        if (STARTS_WITH_DIGIT.matcher(schemaType).matches()) { // starts with number
             return "`" + schemaType + "`";
         } else {
             return schemaType;
@@ -663,12 +667,12 @@ public String toVarName(String name) {
         }
 
         // numbers are not allowed at the beginning
-        if (name.matches("^\\d.*")) {
+        if (STARTS_WITH_DIGIT.matcher(name).matches()) {
             name = "`" + name + "`";
         }
 
         // if it's all upper case, do nothing
-        if (name.matches("^[A-Z0-9_]*$")) {
+        if (ALL_UPPER_UNDERSCORE_DIGITS.matcher(name).matches()) {
             return name;
         }
 
@@ -706,7 +710,7 @@ protected boolean needToImport(String type) {
     public String toEnumName(CodegenProperty property) {
         String name = StringUtils.camelize(property.name);
 
-        if (name.matches("\\d.*")) { // starts with number
+        if (STARTS_WITH_DIGIT.matcher(name).matches()) { // starts with number
             return "`" + name + "`";
         } else {
             return name;
@@ -715,7 +719,7 @@ public String toEnumName(CodegenProperty property) {
 
     private boolean isValidIdentifier(String identifier) {
         //see https://nim-lang.org/docs/manual.html#lexical-analysis-identifiers-amp-keywords
-        return identifier.matches("^(?:[A-Z]|[a-z]|[\\x80-\\xff])(_?(?:[A-Z]|[a-z]|[\\x80-\\xff]|[0-9]))*$");
+        return NIM_TYPE_NAME.matcher(identifier).matches();
     }
 
     /**
@@ -730,9 +734,9 @@ private String sanitizeNimIdentifier(String name) {
             return name;
         }
         // Remove trailing underscores (Nim identifiers cannot end with underscore)
-        name = name.replaceAll("_+$", "");
+        name = MULTI_TRAILING_UNDERSCORES.matcher(name).replaceAll("");
         // Collapse multiple consecutive underscores to single underscore
-        name = name.replaceAll("_+", "_");
+        name = MULTI_UNDERSCORES.matcher(name).replaceAll("_");
         return name;
     }
 
diff --git a/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/NodeJSExpressServerCodegen.java b/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/NodeJSExpressServerCodegen.java
index 61931624de0b..34927e1ec01a 100644
--- a/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/NodeJSExpressServerCodegen.java
+++ b/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/NodeJSExpressServerCodegen.java
@@ -343,12 +343,11 @@ public void preprocessOpenAPI(OpenAPI openAPI) {
             if (info.getTitle() != null) {
                 // when info.title is defined, use it for projectName
                 // used in package.json
-                projectName = info.getTitle()
-                        .replaceAll("[^a-zA-Z0-9]", "-")
-                        .replaceAll("^[-]*", "")
-                        .replaceAll("[-]*$", "")
-                        .replaceAll("[-]{2,}", "-")
-                        .toLowerCase(Locale.ROOT);
+                projectName = NON_ALPHANUMERIC_CHAR.matcher(info.getTitle()).replaceAll("-");
+                projectName = LEADING_HYPHENS.matcher(projectName).replaceAll("");
+                projectName = TRAILING_HYPHENS.matcher(projectName).replaceAll("");
+                projectName = MULTI_HYPHEN.matcher(projectName).replaceAll("-");
+                projectName = projectName.toLowerCase(Locale.ROOT);
                 this.additionalProperties.put("projectName", projectName);
             }
         }
diff --git a/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/OCamlClientCodegen.java b/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/OCamlClientCodegen.java
index c6c8ef3ae866..4e93ba6d44f9 100644
--- a/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/OCamlClientCodegen.java
+++ b/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/OCamlClientCodegen.java
@@ -38,6 +38,7 @@
 
 import java.io.File;
 import java.util.*;
+import java.util.regex.Pattern;
 import java.util.stream.Collectors;
 
 import static org.apache.commons.lang3.StringUtils.capitalize;
@@ -51,6 +52,15 @@ public class OCamlClientCodegen extends DefaultCodegen implements CodegenConfig
 
     static final String X_MODEL_MODULE = "x-model-module";
 
+    /** Matches a model name that starts with a digit or underscore (invalid OCaml identifier start). */
+    private static final Pattern OCAML_INVALID_NAME_START = Pattern.compile("^\\d.*|^_.*");
+    /** Matches a string that does NOT start with a letter or underscore. */
+    private static final Pattern OCAML_INVALID_IDENTIFIER_START = Pattern.compile("^[^a-zA-Z_]");
+    /** Matches a trailing {@code " list"} type suffix in OCaml return types. */
+    private static final Pattern OCAML_LIST_SUFFIX = Pattern.compile(" list$");
+    /** Matches a comma delimiter used to split enum value strings. */
+    private static final Pattern COMMA_DELIMITER = Pattern.compile(",");
+
     @Setter
     protected String packageName = "openapi";
     @Setter
@@ -641,7 +651,7 @@ public String modelFileFolder() {
     @Override
     public String toVarName(String name) {
         // replace - with _ e.g. created-at => created_at
-        name = sanitizeName(name.replaceAll("-", "_"));
+        name = sanitizeName(MINUS.matcher(name).replaceAll("_"));
 
         // snake_case, e.g. PetId => pet_id
         name = underscore(name);
@@ -651,7 +661,7 @@ public String toVarName(String name) {
             name = escapeReservedWord(name);
 
         // for reserved word or word starting with number, append _
-        if (name.matches("^\\d.*"))
+        if (STARTS_WITH_DIGIT.matcher(name).matches())
             name = "var_" + name;
 
         return name;
@@ -689,7 +699,7 @@ public String toModelFilename(String name) {
         }
 
         // model name starts with number or _
-        if (name.matches("^\\d.*|^_.*")) {
+        if (OCAML_INVALID_NAME_START.matcher(name).matches()) {
             LOGGER.warn("{} (model name starts with number) cannot be used as model name. Renamed to {}", name,
                     "model_" + name);
             name = "model_" + name; // e.g. 200Response => Model200Response (after camelize)
@@ -701,7 +711,7 @@ public String toModelFilename(String name) {
     @Override
     public String toApiFilename(final String name) {
         // replace - with _ e.g. created-at => created_at
-        final String _name = name.replaceAll("-", "_");
+        final String _name = MINUS.matcher(name).replaceAll("_");
 
         // e.g. PetApi.ml => pet_api.ml
         return underscore(_name) + "_api";
@@ -791,7 +801,7 @@ public String toOperationId(String operationId) {
         String sanitizedOperationId = sanitizeName(operationId);
 
         // method name cannot use reserved keyword, e.g. return
-        if (isReservedWord(sanitizedOperationId) || sanitizedOperationId.matches("^[0-9].*")) {
+        if (isReservedWord(sanitizedOperationId) || STARTS_WITH_DIGIT.matcher(sanitizedOperationId).matches()) {
             LOGGER.warn("{} (reserved word) cannot be used as method name. Renamed to {}", operationId, underscore("call_" + operationId));
             sanitizedOperationId = "call_" + sanitizedOperationId;
         }
@@ -808,7 +818,7 @@ private Map<String, Object> allowableValues(String valueString) {
     private List<Map<String, Object>> buildEnumValues(String valueString) {
         List<Map<String, Object>> result = new ArrayList<>();
 
-        for (String v : valueString.split(",")) {
+        for (String v : COMMA_DELIMITER.split(valueString)) {
             Map<String, Object> m = new HashMap<>();
             String value = v.isEmpty() ? "empty" : v;
             m.put("name", value);
@@ -834,7 +844,7 @@ private String ocamlizeEnumValue(String value) {
                 toEnumValueName(value.isEmpty() ? "empty" : value)
                         .replace(" ", "_");
 
-        if (!sanitizedValue.matches("^[a-zA-Z_].*")) {
+        if (OCAML_INVALID_IDENTIFIER_START.matcher(sanitizedValue).find()) {
             sanitizedValue = "_" + sanitizedValue;
         }
         return "`" + capitalize(sanitizedValue);
@@ -846,7 +856,7 @@ private CodegenModel buildEnumModel(String enumName, String values) {
         m.setName(enumName);
         m.setClassname(enumName);
         m.setDataType(enumName);
-        String[] vals = values.split(",");
+        String[] vals = COMMA_DELIMITER.split(values);
         if (vals.length == 1) {
             m.setDefaultValue(ocamlizeEnumValue(vals[0]));
         }
@@ -879,7 +889,7 @@ public OperationsMap postProcessOperationsWithModels(OperationsMap objs, List<Mo
             }
 
             if (operation.returnType != null && operation.returnType.startsWith("Enums.")) {
-                String returnTypeEnum = operation.returnType.replaceAll(" list$", "");
+                String returnTypeEnum = OCAML_LIST_SUFFIX.matcher(operation.returnType).replaceAll("");
                 operation.vendorExtensions.put("x-returntype-enum", returnTypeEnum);
                 operation.vendorExtensions.put("x-returntype-is-enum", true);
             }
diff --git a/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/ObjcClientCodegen.java b/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/ObjcClientCodegen.java
index 9c388464071f..29b985fa390b 100644
--- a/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/ObjcClientCodegen.java
+++ b/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/ObjcClientCodegen.java
@@ -26,6 +26,7 @@
 import org.openapitools.codegen.model.OperationMap;
 import org.openapitools.codegen.model.OperationsMap;
 import org.openapitools.codegen.utils.ModelUtils;
+import org.openapitools.codegen.utils.PatternCache;
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
 
@@ -66,6 +67,11 @@ public class ObjcClientCodegen extends DefaultCodegen implements CodegenConfig {
 
     protected Set<String> advancedMappingTypes = new HashSet<>();
 
+    /** Matches any character that is not alphanumeric or underscore; used in model name normalization. */
+    private static final java.util.regex.Pattern NON_ALNUM_UNDERSCORE = java.util.regex.Pattern.compile("[^0-9a-zA-Z_]");
+    /** Matches a single uppercase letter or underscore only (e.g. {@code "A"}, {@code "_"}). */
+    private static final java.util.regex.Pattern SINGLE_UPPER_OR_UNDERSCORE = java.util.regex.Pattern.compile("^[A-Z_]$");
+
     public ObjcClientCodegen() {
         super();
 
@@ -445,7 +451,7 @@ public String toModelName(String type) {
 
         // model name starts with number
         /* no need for the fix below as objc model starts with prefix (e.g. SWG)
-        if (type.matches("^\\d.*")) {
+        if (STARTS_WITH_DIGIT.matcher(type).matches()) {
             LOGGER.warn(type + " (model name starts with number) cannot be used as model name. Renamed to " + camelize("model_" + type));
             type = "model_" + type; // e.g. 200Response => Model200Response (after camelize)
         }
@@ -462,7 +468,7 @@ public String toModelName(String type) {
      * @return model Name in ObjC style guide
      */
     public String toModelNameWithoutReservedWordCheck(String type) {
-        type = type.replaceAll("[^0-9a-zA-Z_]", "_"); // FIXME: a parameter should not be assigned. Also declare the methods parameters as 'final'.
+        type = NON_ALNUM_UNDERSCORE.matcher(type).replaceAll("_"); // FIXME: a parameter should not be assigned. Also declare the methods parameters as 'final'.
 
         // language build-in classes
         if (typeMapping.keySet().contains(type) ||
@@ -557,18 +563,18 @@ public String toVarName(String name) {
         name = sanitizeName(name); // FIXME: a parameter should not be assigned. Also declare the methods parameters as 'final'.
 
         // if it's all upper case, do noting
-        if (name.matches("^[A-Z_]$")) {
+        if (SINGLE_UPPER_OR_UNDERSCORE.matcher(name).matches()) {
             return name;
         }
 
         // if name starting with special word, escape with '_'
         for (String specialWord : specialWords) {
-            if (name.matches("(?i:^" + specialWord + ".*)"))
+            if (PatternCache.get("(?i:^" + specialWord + ".*)").matcher(name).matches())
                 name = escapeSpecialWord(name);
         }
 
         if (name.startsWith(classPrefix)) {
-            name = name.replaceFirst(classPrefix, ""); //remove the class prefix, e.g. SWGPet => Pet
+            name = PatternCache.get(java.util.regex.Pattern.quote(classPrefix)).matcher(name).replaceFirst(""); //remove the class prefix, e.g. SWGPet => Pet
         }
 
         // camelize (lower first character) the variable name
@@ -576,7 +582,7 @@ public String toVarName(String name) {
         name = camelize(name, LOWERCASE_FIRST_LETTER);
 
         // for reserved word or word starting with number, prepend `_`
-        if (isReservedWord(name) || name.matches("^\\d.*")) {
+        if (isReservedWord(name) || STARTS_WITH_DIGIT.matcher(name).matches()) {
             name = escapeReservedWord(name);
         }
 
diff --git a/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/PerlClientCodegen.java b/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/PerlClientCodegen.java
index 95cd04247ccc..f1c3226f868b 100644
--- a/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/PerlClientCodegen.java
+++ b/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/PerlClientCodegen.java
@@ -330,7 +330,7 @@ public String toVarName(String name) {
 
         // parameter name starting with number won't compile
         // need to escape it by appending _ at the beginning
-        if (name.matches("^\\d.*")) {
+        if (STARTS_WITH_DIGIT.matcher(name).matches()) {
             name = "_" + name;
         }
         return name;
@@ -375,7 +375,7 @@ public String toModelName(String name) {
         }
 
         // model name starts with number
-        if (name.matches("^\\d.*")) {
+        if (STARTS_WITH_DIGIT.matcher(name).matches()) {
             LOGGER.warn("{} (model name starts with number) cannot be used as model name. Renamed to {}", name,
                     camelize("model_" + name));
             name = "model_" + name; // e.g. 200Response => Model200Response (after camelize)
@@ -426,7 +426,7 @@ public String toApiDocFilename(String name) {
     @Override
     public String toApiFilename(String name) {
         // replace - with _ e.g. created-at => created_at
-        name = name.replaceAll("-", "_"); // FIXME: a parameter should not be assigned. Also declare the methods parameters as 'final'.
+        name = MINUS.matcher(name).replaceAll("_"); // FIXME: a parameter should not be assigned. Also declare the methods parameters as 'final'.
 
         // e.g. phone_number_api.rb => PhoneNumberApi.rb
         return camelize(name) + "Api";
@@ -457,7 +457,7 @@ public String toOperationId(String operationId) {
         }
 
         // operationId starts with a number
-        if (operationId.matches("^\\d.*")) {
+        if (STARTS_WITH_DIGIT.matcher(operationId).matches()) {
             LOGGER.warn("{} (starting with a number) cannot be used as method name. Renamed to {}", operationId, underscore(sanitizeName("call_" + operationId)));
             operationId = "call_" + operationId;
         }
diff --git a/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/PhpFlightServerCodegen.java b/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/PhpFlightServerCodegen.java
index bd35553b9834..b14617bd54be 100644
--- a/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/PhpFlightServerCodegen.java
+++ b/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/PhpFlightServerCodegen.java
@@ -207,7 +207,7 @@ public OperationsMap postProcessOperationsWithModels(OperationsMap objs, List<Mo
     }
 
     private String mapToFlightPath(String path) {
-        return path.replaceAll("\\{([^}]+)}", "@$1");
+        return PATH_PARAMETER.matcher(path).replaceAll("@$1");
     }
 
     @Override
diff --git a/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/PhpSilexServerCodegen.java b/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/PhpSilexServerCodegen.java
index d0ae87c514d6..0c6bf0c97821 100644
--- a/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/PhpSilexServerCodegen.java
+++ b/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/PhpSilexServerCodegen.java
@@ -217,7 +217,7 @@ public String toVarName(String name) {
 
         // parameter name starting with number won't compile
         // need to escape it by appending _ at the beginning
-        if (name.matches("^\\d.*")) {
+        if (STARTS_WITH_DIGIT.matcher(name).matches()) {
             name = "_" + name;
         }
 
diff --git a/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/PhpSlim4ServerCodegen.java b/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/PhpSlim4ServerCodegen.java
index a1822fe72e23..33725abf475e 100644
--- a/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/PhpSlim4ServerCodegen.java
+++ b/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/PhpSlim4ServerCodegen.java
@@ -29,6 +29,7 @@
 import org.openapitools.codegen.model.ModelMap;
 import org.openapitools.codegen.model.OperationMap;
 import org.openapitools.codegen.model.OperationsMap;
+import org.openapitools.codegen.utils.PatternCache;
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
 
@@ -60,6 +61,17 @@ public class PhpSlim4ServerCodegen extends AbstractPhpCodegen {
     protected String interfacesDirName = "Interfaces";
     protected String interfacesPackage = "";
 
+    /** Precompiled patterns for URL-encoding fixups in {@link #encodePath}. */
+    private static final java.util.regex.Pattern URL_ENC_PLUS      = java.util.regex.Pattern.compile("\\+");
+    private static final java.util.regex.Pattern URL_ENC_SLASH     = java.util.regex.Pattern.compile("%2F", java.util.regex.Pattern.CASE_INSENSITIVE);
+    private static final java.util.regex.Pattern URL_ENC_OPEN_CB   = java.util.regex.Pattern.compile("%7B", java.util.regex.Pattern.CASE_INSENSITIVE);
+    private static final java.util.regex.Pattern URL_ENC_CLOSE_CB  = java.util.regex.Pattern.compile("%7D", java.util.regex.Pattern.CASE_INSENSITIVE);
+    private static final java.util.regex.Pattern URL_ENC_OPEN_SB   = java.util.regex.Pattern.compile("%5B", java.util.regex.Pattern.CASE_INSENSITIVE);
+    private static final java.util.regex.Pattern URL_ENC_CLOSE_SB  = java.util.regex.Pattern.compile("%5D", java.util.regex.Pattern.CASE_INSENSITIVE);
+    private static final java.util.regex.Pattern URL_ENC_COLON     = java.util.regex.Pattern.compile("%3A", java.util.regex.Pattern.CASE_INSENSITIVE);
+    private static final java.util.regex.Pattern URL_ENC_PLUS_SIGN = java.util.regex.Pattern.compile("%2B", java.util.regex.Pattern.CASE_INSENSITIVE);
+    private static final java.util.regex.Pattern URL_ENC_BACKSLASH_D = java.util.regex.Pattern.compile("%5C%5Cd", java.util.regex.Pattern.CASE_INSENSITIVE);
+
     public PhpSlim4ServerCodegen() {
         super();
 
@@ -316,8 +328,8 @@ public String toApiTestFilename(String name) {
      */
     private void addUserClassnameToOperations(OperationMap operations) {
         String classname = operations.getClassname();
-        classname = classname.replaceAll("^" + abstractNamePrefix, "");
-        classname = classname.replaceAll(abstractNameSuffix + "$", "");
+        classname = PatternCache.get("^" + abstractNamePrefix).matcher(classname).replaceAll("");
+        classname = PatternCache.get(abstractNameSuffix + "$").matcher(classname).replaceAll("");
         operations.put(USER_CLASSNAME_KEY, classname);
     }
 
@@ -334,10 +346,10 @@ public String encodePath(String input) {
         // outer unescape to retain the original multi-byte characters
         // finally escalate characters avoiding code injection
         input = super.escapeUnsafeCharacters(
-                StringEscapeUtils.unescapeJava(
+                CONTROL_WHITESPACE.matcher(StringEscapeUtils.unescapeJava(
                                 StringEscapeUtils.escapeJava(input)
-                                        .replace("\\/", "/"))
-                        .replaceAll("[\\t\\n\\r]", " ")
+                                        .replace("\\/", "/")))
+                        .replaceAll(" ")
                         .replace("\\", "\\\\"));
         // .replace("\"", "\\\""));
 
@@ -345,16 +357,25 @@ public String encodePath(String input) {
         // Trim the string to avoid leading and trailing spaces.
         input = input.trim();
 
-        return URLEncoder.encode(input, StandardCharsets.UTF_8)
-                .replaceAll("\\+", "%20")
-                .replaceAll("\\%2F", "/")
-                .replaceAll("\\%7B", "{") // keep { part of complex placeholders
-                .replaceAll("\\%7D", "}") // } part
-                .replaceAll("\\%5B", "[") // [ part
-                .replaceAll("\\%5D", "]") // ] part
-                .replaceAll("\\%3A", ":") // : part
-                .replaceAll("\\%2B", "+") // + part
-                .replaceAll("\\%5C\\%5Cd", "\\\\d"); // \d part
+        return URL_ENC_BACKSLASH_D.matcher(
+               URL_ENC_PLUS_SIGN.matcher(
+               URL_ENC_COLON.matcher(
+               URL_ENC_CLOSE_SB.matcher(
+               URL_ENC_OPEN_SB.matcher(
+               URL_ENC_CLOSE_CB.matcher(
+               URL_ENC_OPEN_CB.matcher(
+               URL_ENC_SLASH.matcher(
+               URL_ENC_PLUS.matcher(
+                   URLEncoder.encode(input, StandardCharsets.UTF_8))
+                   .replaceAll("%20"))
+                   .replaceAll("/"))
+                   .replaceAll("{"))
+                   .replaceAll("}"))
+                   .replaceAll("["))
+                   .replaceAll("]"))
+                   .replaceAll(":"))
+                   .replaceAll("+"))
+                   .replaceAll("\\\\d");
     }
 
     @Override
diff --git a/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/PostgresqlSchemaCodegen.java b/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/PostgresqlSchemaCodegen.java
index 8630b4bb303c..b6c51c5ae4c6 100644
--- a/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/PostgresqlSchemaCodegen.java
+++ b/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/PostgresqlSchemaCodegen.java
@@ -38,6 +38,8 @@
 @SuppressWarnings("unchecked")
 public class PostgresqlSchemaCodegen extends DefaultCodegen {
     private final Logger LOGGER = LoggerFactory.getLogger(PostgresqlSchemaCodegen.class);
+    private static final Pattern UNSAFE_UNQUOTED_IDENTIFIER_CHARS = Pattern.compile("[^0-9a-zA-Z$_\\u0080-\\uFFFF]");
+    private static final Pattern UNSAFE_QUOTED_IDENTIFIER_CHARS = Pattern.compile("[^\\u0001-\\u007F\\u0080-\\uFFFF]");
 
     public static final String VENDOR_EXTENSION_POSTGRESQL_SCHEMA = "x-postgresql-schema";
     public static final String DEFAULT_DATABASE_NAME = "defaultDatabaseName";
@@ -1317,14 +1319,14 @@ public String toColumnName(String name) {
     public String toPostgresqlIdentifier(String name, String prefix, String suffix) {
         String escapedName = escapePostgresqlQuotedIdentifier(name);
         // Database, table, and column names cannot end with space characters.
-        if (escapedName.matches(".*\\s$")) {
+        if (ENDS_WITH_WHITESPACE.matcher(escapedName).matches()) {
             LOGGER.warn("Database, table, and column names cannot end with space characters. Check '{}' name", name);
-            escapedName = escapedName.replaceAll("\\s+$", "");
+            escapedName = TRAILING_WHITESPACE.matcher(escapedName).replaceAll("");
         }
 
         // Identifiers may begin with a digit but unless quoted may not consist solely
         // of digits.
-        if (escapedName.matches("^\\d+$")) {
+        if (DIGITS_ONLY.matcher(escapedName).matches()) {
             LOGGER.warn("Database, table, and column names cannot consist solely of digits. Check '{}' name", name);
             escapedName = prefix + escapedName + suffix;
         }
@@ -1346,12 +1348,11 @@ public String toPostgresqlIdentifier(String name, String prefix, String suffix)
     public String escapePostgresqlUnquotedIdentifier(String identifier) {
         // ASCII: [0-9,a-z,A-Z$_] (basic Latin letters, digits 0-9, dollar, underscore)
         // Extended: U+0080 .. U+FFFF
-        Pattern regexp = Pattern.compile("[^0-9a-zA-z$_\\u0080-\\uFFFF]");
-        Matcher matcher = regexp.matcher(identifier);
+        Matcher matcher = UNSAFE_UNQUOTED_IDENTIFIER_CHARS.matcher(identifier);
         if (matcher.find()) {
             LOGGER.warn("Identifier '{}' contains unsafe characters out of [0-9,a-z,A-Z$_] and U+0080..U+FFFF range",
                     identifier);
-            identifier = identifier.replaceAll("[^0-9a-zA-z$_\\u0080-\\uFFFF]", "");
+            identifier = matcher.reset().replaceAll("");
         }
 
         // ASCII NUL (U+0000) and supplementary characters (U+10000 and higher) are not
@@ -1371,12 +1372,11 @@ public String escapePostgresqlUnquotedIdentifier(String identifier) {
      */
     public String escapePostgresqlQuotedIdentifier(String identifier) {
         // ASCII: U+0001 .. U+007F Extended: U+0080 .. U+FFFF
-        Pattern regexp = Pattern.compile("[^\\u0001-\\u007F\\u0080-\\uFFFF]");
-        Matcher matcher = regexp.matcher(identifier);
+        Matcher matcher = UNSAFE_QUOTED_IDENTIFIER_CHARS.matcher(identifier);
         if (matcher.find()) {
             LOGGER.warn("Identifier '{}' contains unsafe characters out of U+0001..U+007F and U+0080..U+FFFF range",
                     identifier);
-            identifier = identifier.replaceAll("[^\\u0001-\\u007F\\u0080-\\uFFFF]", "");
+            identifier = matcher.reset().replaceAll("");
         }
 
         // ASCII NUL (U+0000) and supplementary characters (U+10000 and higher) are not
@@ -1458,7 +1458,7 @@ public String toSrcPath(String packageName) {
         // Trim prefix file separators from package path
         String packagePath = StringUtils.removeStart(
                 // Replace period, backslash, forward slash with file separator in package name
-                packageName.replaceAll("[\\.\\\\/]", Matcher.quoteReplacement("/")),
+                PACKAGE_SEPARATOR.matcher(packageName).replaceAll(Matcher.quoteReplacement("/")),
                 File.separator);
 
         // Trim trailing file separators from the overall path
diff --git a/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/PostmanCollectionCodegen.java b/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/PostmanCollectionCodegen.java
index 124bc29b7933..012c31c40ba6 100644
--- a/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/PostmanCollectionCodegen.java
+++ b/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/PostmanCollectionCodegen.java
@@ -34,6 +34,9 @@ public class PostmanCollectionCodegen extends DefaultCodegen implements CodegenC
 
     private final Logger LOGGER = LoggerFactory.getLogger(PostmanCollectionCodegen.class);
 
+    /** Matches Postman double-brace placeholders, e.g. {@code {{variable}}}. */
+    private static final Pattern POSTMAN_PLACEHOLDER_PATTERN = Pattern.compile("\\{\\{([^}]*)}}");
+
     protected String apiVersion = "1.0.0";
 
     // Select whether to create folders according to the spec’s paths or tags. Values: Paths | Tags
@@ -702,8 +705,7 @@ String escapeJsonString(String value) {
     public Set<String> extractPlaceholders(String input) {
         Set<String> variables = new HashSet<>();
 
-        Pattern pattern = Pattern.compile("\\{\\{([^}]*)\\}\\}");
-        Matcher matcher = pattern.matcher(input);
+        Matcher matcher = POSTMAN_PLACEHOLDER_PATTERN.matcher(input);
 
         while (matcher.find()) {
             if (postmanGuidPlaceholderName.equalsIgnoreCase(matcher.group(1))) {
diff --git a/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/PowerShellClientCodegen.java b/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/PowerShellClientCodegen.java
index d0c603d20a07..8c9448f307bc 100644
--- a/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/PowerShellClientCodegen.java
+++ b/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/PowerShellClientCodegen.java
@@ -42,6 +42,11 @@
 
 public class PowerShellClientCodegen extends DefaultCodegen implements CodegenConfig {
     private final Logger LOGGER = LoggerFactory.getLogger(PowerShellClientCodegen.class);
+
+    /** Captures the last path segment of a URL (for extracting PS Gallery package ID). */
+    private static final java.util.regex.Pattern GALLERY_URL_LAST_SEGMENT = java.util.regex.Pattern.compile(".*/([^/?]+).*");
+    /** Matches two or more consecutive newlines — for normalising example output. */
+    private static final java.util.regex.Pattern MULTI_NEWLINE = java.util.regex.Pattern.compile("[\n]{2,}");
     @Setter private String packageGuid = "{" + randomUUID().toString().toUpperCase(Locale.ROOT) + "}";
 
 
@@ -702,7 +707,7 @@ public void processOpts() {
         if (StringUtils.isNotBlank(powershellGalleryUrl)) {
             // get the last segment of the URL
             // e.g. https://www.powershellgallery.com/packages/PSTwitter => PSTwitter
-            additionalProperties.put("powershellGalleryId", powershellGalleryUrl.replaceFirst(".*/([^/?]+).*", "$1"));
+            additionalProperties.put("powershellGalleryId", GALLERY_URL_LAST_SEGMENT.matcher(powershellGalleryUrl).replaceFirst("$1"));
         }
 
         if (additionalProperties.containsKey(CodegenConstants.OPTIONAL_PROJECT_GUID)) {
@@ -798,10 +803,10 @@ public String escapeText(String input) {
         // outer unescape to retain the original multi-byte characters
         // finally escalate characters avoiding code injection
         return escapeUnsafeCharacters(
-                StringEscapeUtils.unescapeJava(
+                CONTROL_WHITESPACE.matcher(StringEscapeUtils.unescapeJava(
                                 StringEscapeUtils.escapeJava(input)
-                                        .replace("\\/", "/"))
-                        .replaceAll("[\\t\\n\\r]", " ")
+                                        .replace("\\/", "/")))
+                        .replaceAll(" ")
                         .replace("\"", "\"\""));
 
     }
@@ -909,7 +914,7 @@ public String toModelName(String name) {
         }
 
         // model name starts with number
-        if (name.matches("^\\d.*")) {
+        if (STARTS_WITH_DIGIT.matcher(name).matches()) {
             LOGGER.warn("{} (model name starts with number) cannot be used as model name. Renamed to {}", name,
                     camelize("model_" + name));
             name = camelize("model_" + name); // e.g. 200Response => Model200Response (after camelize)
@@ -992,7 +997,7 @@ public String toParamName(String name) {
         name = camelize(sanitizeName(name));
 
         // for param name reserved word or word starting with number, append _
-        if (paramNameReservedWords.contains(name) || name.matches("^\\d.*")) {
+        if (paramNameReservedWords.contains(name) || STARTS_WITH_DIGIT.matcher(name).matches()) {
             LOGGER.warn("{} (reserved word or special variable name) cannot be used in naming. Renamed to {}", name,
                     escapeReservedWord(name));
             name = escapeReservedWord(name);
@@ -1127,7 +1132,7 @@ public String toVarName(String name) {
         name = camelize(name);
 
         // for reserved word or word starting with number, append _
-        if (isReservedWord(name) || name.matches("^\\d.*")) {
+        if (isReservedWord(name) || STARTS_WITH_DIGIT.matcher(name).matches()) {
             LOGGER.warn("{} (reserved word or special variable name) cannot be used in naming. Renamed to {}", name,
                     escapeReservedWord(name));
             name = escapeReservedWord(name);
@@ -1202,7 +1207,7 @@ private String constructExampleCode(CodegenParameter codegenParameter, HashMap<S
         }
 
         // Replace multiple new lines with a single new line and trim leading and trailing spaces.
-        return example.toString().replaceAll("[\n]{2,}", "\n\n").trim();
+        return MULTI_NEWLINE.matcher(example.toString()).replaceAll("\n\n").trim();
     }
 
     private String constructExampleCode(CodegenProperty codegenProperty, HashMap<String, CodegenModel> modelMaps, HashMap<String, Integer> processedModelMap, boolean requiredOnly) {
@@ -1541,9 +1546,9 @@ public String toEnumVarName(String name, String datatype) {
                 "UInt16".equals(datatype) || "UInt32".equals(datatype) || "UInt64".equals(datatype) ||
                 "Double".equals(datatype) || "Single".equals(datatype) || "Decimal".equals(datatype)) {
             String varName = name;
-            varName = varName.replaceAll("-", "MINUS_");
-            varName = varName.replaceAll("\\+", "PLUS_");
-            varName = varName.replaceAll("\\.", "_DOT_");
+            varName = MINUS.matcher(varName).replaceAll("MINUS_");
+            varName = PLUS.matcher(varName).replaceAll("PLUS_");
+            varName = DOT.matcher(varName).replaceAll("_DOT_");
             return "NUMBER_" + varName;
         }
 
diff --git a/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/ProtobufSchemaCodegen.java b/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/ProtobufSchemaCodegen.java
index 9e1b641b6e9d..023d3e302165 100644
--- a/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/ProtobufSchemaCodegen.java
+++ b/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/ProtobufSchemaCodegen.java
@@ -16,6 +16,7 @@
 
 package org.openapitools.codegen.languages;
 
+import com.google.common.base.CaseFormat;
 import io.swagger.v3.oas.models.OpenAPI;
 import io.swagger.v3.oas.models.media.ArraySchema;
 import io.swagger.v3.oas.models.media.MapSchema;
@@ -42,12 +43,10 @@
 import java.io.File;
 import java.util.*;
 import java.util.Map.Entry;
-import java.util.regex.Pattern;
 import java.util.stream.Collectors;
 
-import com.google.common.base.CaseFormat;
-
-import static org.openapitools.codegen.utils.StringUtils.*;
+import static org.openapitools.codegen.utils.StringUtils.camelize;
+import static org.openapitools.codegen.utils.StringUtils.underscore;
 
 public class ProtobufSchemaCodegen extends DefaultCodegen implements CodegenConfig {
 
@@ -1545,7 +1544,7 @@ public String toDefaultValue(Schema p) {
             }
         } else if (ModelUtils.isStringSchema(p)) {
             if (p.getDefault() != null) {
-                if (Pattern.compile("\r\n|\r|\n").matcher(String.valueOf(p.getDefault())).find())
+                if (MULTILINE_STRING.matcher(String.valueOf(p.getDefault())).find())
                     return "'''" + p.getDefault() + "'''";
                 else
                     return "'" + p.getDefault() + "'";
@@ -1572,7 +1571,7 @@ public String modelFileFolder() {
     @Override
     public String toApiFilename(String name) {
         // replace - with _ e.g. created-at => created_at
-        name = name.replaceAll("-", "_");
+        name = MINUS.matcher(name).replaceAll("_");
 
         // e.g. PhoneNumber => phone_number
         return underscore(name) + "_service";
@@ -1611,7 +1610,7 @@ public String toVarName(String name) {
         name = sanitizeName(name); // FIXME: a parameter should not be assigned. Also declare the methods parameters as 'final'.
 
         // if it's all upper case, convert to lower case
-        if (name.matches("^[A-Z_]*$")) {
+        if (ALL_UPPER_UNDERSCORE.matcher(name).matches()) {
             name = name.toLowerCase(Locale.ROOT);
         }
 
@@ -1620,10 +1619,10 @@ public String toVarName(String name) {
         name = underscore(name);
 
         // remove leading underscore
-        name = name.replaceAll("^_*", "");
+        name = LEADING_UNDERSCORES.matcher(name).replaceAll("");
 
         // for reserved word or word starting with number, append _
-        if (isReservedWord(name) || name.matches("^\\d.*")) {
+        if (isReservedWord(name) || STARTS_WITH_DIGIT.matcher(name).matches()) {
             name = escapeReservedWord(name);
         }
 
@@ -1648,7 +1647,7 @@ public String toModelName(String name) {
         }
 
         // model name starts with number
-        if (name.matches("^\\d.*")) {
+        if (STARTS_WITH_DIGIT.matcher(name).matches()) {
             LOGGER.warn("{} (model name starts with number) cannot be used as model name. Renamed to {}", name,
                     camelize("model_" + name));
             name = "model_" + name; // e.g. 200Response => Model200Response (after camelize)
@@ -1809,7 +1808,7 @@ private int generateFieldNumberFromString(String name) throws ProtoBufIndexCompu
         // Max value from developers.google.com/protocol-buffers/docs/proto3#assigning_field_numbers
         int fieldNumber = Math.abs(name.hashCode() % 536870911);
         if (19000 <= fieldNumber && fieldNumber <= 19999) {
-            LOGGER.error("Generated field number is in reserved range (19000, 19999) for %s, %d", name, fieldNumber);
+            LOGGER.error("Generated field number is in reserved range (19000, 19999) for {}, {}", name, fieldNumber);
             throw new ProtoBufIndexComputationException("Generated field number is in reserved range (19000, 19999).");
         }
         return fieldNumber;
diff --git a/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/PythonClientCodegen.java b/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/PythonClientCodegen.java
index 924263f217b3..8ed782c63cdf 100644
--- a/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/PythonClientCodegen.java
+++ b/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/PythonClientCodegen.java
@@ -310,7 +310,7 @@ public void processOpts() {
         }
 
         // If the package name consists of dots(openapi.client), then we need to create the directory structure like openapi/client with __init__ files.
-        String[] packageNameSplits = packageName.split("\\.");
+        String[] packageNameSplits = DOT.split(packageName);
         String currentPackagePath = "";
         for (int i = 0; i < packageNameSplits.length - 1; i++) {
             if (i > 0) {
diff --git a/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/PythonPydanticV1ClientCodegen.java b/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/PythonPydanticV1ClientCodegen.java
index 0834b51cd4cf..bb3178be50ba 100644
--- a/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/PythonPydanticV1ClientCodegen.java
+++ b/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/PythonPydanticV1ClientCodegen.java
@@ -314,7 +314,7 @@ public void processOpts() {
         }
 
         // If the package name consists of dots(openapi.client), then we need to create the directory structure like openapi/client with __init__ files.
-        String[] packageNameSplits = packageName.split("\\.");
+        String[] packageNameSplits = DOT.split(packageName);
         String currentPackagePath = "";
         for (int i = 0; i < packageNameSplits.length - 1; i++) {
             if (i > 0) {
diff --git a/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/RClientCodegen.java b/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/RClientCodegen.java
index 188436a75eb5..dd06b7cc7fb4 100644
--- a/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/RClientCodegen.java
+++ b/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/RClientCodegen.java
@@ -38,7 +38,6 @@
 import java.io.IOException;
 import java.io.Writer;
 import java.util.*;
-import java.util.regex.Pattern;
 
 import static org.openapitools.codegen.utils.CamelizeOption.LOWERCASE_FIRST_LETTER;
 import static org.openapitools.codegen.utils.StringUtils.camelize;
@@ -400,10 +399,10 @@ public String toParamName(String name) {
         }
 
         // replace - with _ e.g. created-at => created_at
-        name = sanitizeName(name.replaceAll("-", "_"));
+        name = sanitizeName(MINUS.matcher(name).replaceAll("_"));
 
         // if it's all upper case, do nothing
-        if (name.matches("^[A-Z_]*$"))
+        if (ALL_UPPER_UNDERSCORE.matcher(name).matches())
             return name;
 
         // convert variable name to snake case
@@ -415,7 +414,7 @@ public String toParamName(String name) {
             name = "var_" + name;
 
         // for reserved word or word starting with number, append _
-        if (name.matches("^\\d.*"))
+        if (STARTS_WITH_DIGIT.matcher(name).matches())
             name = "var_" + name;
 
         return name;
@@ -489,7 +488,7 @@ public String toModelName(String name) {
         }
 
         // model name starts with number
-        if (name.matches("^\\d.*")) {
+        if (STARTS_WITH_DIGIT.matcher(name).matches()) {
             LOGGER.warn("{} (model name starts with number) cannot be used as model name. Renamed to {}", name,
                     camelize("model_" + name));
             name = "model_" + name; // e.g. 200Response => Model200Response (after camelize)
@@ -502,7 +501,7 @@ public String toModelName(String name) {
     @Override
     public String toApiFilename(String name) {
         // replace - with _ e.g. created-at => created_at
-        name = name.replaceAll("-", "_"); // FIXME: a parameter should not be assigned. Also declare the methods parameters as 'final'.
+        name = MINUS.matcher(name).replaceAll("_"); // FIXME: a parameter should not be assigned. Also declare the methods parameters as 'final'.
 
         // e.g. PetApi.r => pet_api.r
         return underscore(name + "_api");
@@ -710,9 +709,9 @@ public String toEnumVarName(String name, String datatype) {
         // number
         if ("int".equals(datatype) || "double".equals(datatype) || "float".equals(datatype)) {
             String varName = name;
-            varName = varName.replaceAll("-", "MINUS_");
-            varName = varName.replaceAll("\\+", "PLUS_");
-            varName = varName.replaceAll("\\.", "_DOT_");
+            varName = MINUS.matcher(varName).replaceAll("MINUS_");
+            varName = PLUS.matcher(varName).replaceAll("PLUS_");
+            varName = DOT.matcher(varName).replaceAll("_DOT_");
             return varName;
         }
 
@@ -723,10 +722,10 @@ public String toEnumVarName(String name, String datatype) {
 
         // string
         String enumName = sanitizeName(underscore(name).toUpperCase(Locale.ROOT));
-        enumName = enumName.replaceFirst("^_", "");
-        enumName = enumName.replaceFirst("_$", "");
+        enumName = FIRST_LEADING_UNDERSCORE.matcher(enumName).replaceFirst("");
+        enumName = LAST_TRAILING_UNDERSCORE.matcher(enumName).replaceFirst("");
 
-        if (isReservedWord(enumName) || enumName.matches("\\d.*")) { // reserved word or starts with number
+        if (isReservedWord(enumName) || STARTS_WITH_DIGIT.matcher(enumName).matches()) { // reserved word or starts with number
             return escapeReservedWord(enumName);
         } else {
             return enumName;
@@ -740,7 +739,7 @@ public String toEnumName(CodegenProperty property) {
         // remove [] for array or map of enum
         enumName = enumName.replace("[]", "");
 
-        if (enumName.matches("\\d.*")) { // starts with number
+        if (STARTS_WITH_DIGIT.matcher(enumName).matches()) { // starts with number
             return "_" + enumName;
         } else {
             return enumName;
@@ -859,7 +858,7 @@ public String toDefaultValue(Schema p) {
             }
         } else if (ModelUtils.isStringSchema(p)) {
             if (p.getDefault() != null) {
-                if (Pattern.compile("\r\n|\r|\n").matcher((String.valueOf(p.getDefault()))).find())
+                if (MULTILINE_STRING.matcher((String.valueOf(p.getDefault()))).find())
                     return "'''" + p.getDefault().toString() + "'''";
                 else
                     return "\"" + ((String.valueOf(p.getDefault()))).replaceAll("\"", "\\\"") + "\"";
diff --git a/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/RubyClientCodegen.java b/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/RubyClientCodegen.java
index bd8595749bb2..328be26b8dd1 100644
--- a/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/RubyClientCodegen.java
+++ b/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/RubyClientCodegen.java
@@ -340,7 +340,7 @@ public String getHelp() {
      */
     @SuppressWarnings("static-method")
     public String generateModuleName(String gemName) {
-        return camelize(gemName.replaceAll("[^\\w]+", "_"));
+        return camelize(NON_WORD_PLUS.matcher(gemName).replaceAll("_"));
     }
 
     /**
@@ -351,7 +351,7 @@ public String generateModuleName(String gemName) {
      */
     @SuppressWarnings("static-method")
     public String generateGemName(String moduleName) {
-        return underscore(moduleName.replaceAll("[^\\w]+", ""));
+        return underscore(NON_WORD_PLUS.matcher(moduleName).replaceAll(""));
     }
 
     @Override
@@ -442,7 +442,7 @@ public String toModelName(final String name) {
         }
 
         // model name starts with number
-        if (modelName.matches("^\\d.*")) {
+        if (STARTS_WITH_DIGIT.matcher(modelName).matches()) {
             LOGGER.warn("{} (model name starts with number) cannot be used as model name. Renamed to {}", modelName,
                     camelize("model_" + modelName));
             modelName = "model_" + modelName; // e.g. 200Response => Model200Response (after camelize)
@@ -524,10 +524,10 @@ public String toEnumVarName(String name, String datatype) {
 
         // string
         String enumName = sanitizeName(underscore(name).toUpperCase(Locale.ROOT));
-        enumName = enumName.replaceFirst("^_", "");
-        enumName = enumName.replaceFirst("_$", "");
+        enumName = FIRST_LEADING_UNDERSCORE.matcher(enumName).replaceFirst("");
+        enumName = LAST_TRAILING_UNDERSCORE.matcher(enumName).replaceFirst("");
 
-        if (enumName.matches("\\d.*")) { // starts with number
+        if (STARTS_WITH_DIGIT.matcher(enumName).matches()) { // starts with number
             return NUMERIC_ENUM_PREFIX + enumName;
         } else {
             return enumName;
@@ -541,10 +541,10 @@ public String toEnumName(CodegenProperty property) {
         }
 
         String enumName = underscore(toModelName(property.name)).toUpperCase(Locale.ROOT);
-        enumName = enumName.replaceFirst("^_", "");
-        enumName = enumName.replaceFirst("_$", "");
+        enumName = FIRST_LEADING_UNDERSCORE.matcher(enumName).replaceFirst("");
+        enumName = LAST_TRAILING_UNDERSCORE.matcher(enumName).replaceFirst("");
 
-        if (enumName.matches("\\d.*")) { // starts with number
+        if (STARTS_WITH_DIGIT.matcher(enumName).matches()) { // starts with number
             return NUMERIC_ENUM_PREFIX + enumName;
         } else {
             return enumName;
@@ -574,7 +574,7 @@ public String toOperationId(String operationId) {
         }
 
         // operationId starts with a number
-        if (operationId.matches("^\\d.*")) {
+        if (STARTS_WITH_DIGIT.matcher(operationId).matches()) {
             LOGGER.warn("{} (starting with a number) cannot be used as method name. Renamed to {}", operationId, underscore(sanitizeName("call_" + operationId)));
             operationId = "call_" + operationId;
         }
diff --git a/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/RubyOnRailsServerCodegen.java b/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/RubyOnRailsServerCodegen.java
index b3f484f375cd..e4db03a7668f 100644
--- a/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/RubyOnRailsServerCodegen.java
+++ b/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/RubyOnRailsServerCodegen.java
@@ -265,7 +265,7 @@ public String toModelFilename(String name) {
     @Override
     public String toApiFilename(String name) {
         // replace - with _ e.g. created-at => created_at
-        name = name.replaceAll("-", "_"); // FIXME: a parameter should not be assigned. Also declare the methods parameters as 'final'.
+        name = MINUS.matcher(name).replaceAll("_"); // FIXME: a parameter should not be assigned. Also declare the methods parameters as 'final'.
 
         // e.g. DefaultController => defaults_controller.rb
         return underscore(name) + "_controller";
diff --git a/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/RubySinatraServerCodegen.java b/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/RubySinatraServerCodegen.java
index 1e51a349e0db..c32e2e70db57 100644
--- a/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/RubySinatraServerCodegen.java
+++ b/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/RubySinatraServerCodegen.java
@@ -157,7 +157,7 @@ public String toModelFilename(String name) {
     @Override
     public String toApiFilename(String name) {
         // replace - with _ e.g. created-at => created_at
-        name = name.replaceAll("-", "_"); // FIXME: a parameter should not be assigned. Also declare the methods parameters as 'final'.
+        name = MINUS.matcher(name).replaceAll("_"); // FIXME: a parameter should not be assigned. Also declare the methods parameters as 'final'.
 
         // e.g. PhoneNumberApi.rb => phone_number_api.rb
         return underscore(name) + "_api";
@@ -165,7 +165,7 @@ public String toApiFilename(String name) {
 
     @Override
     public String toApiName(String name) {
-        if (name.length() == 0) {
+        if (name.isEmpty()) {
             return "DefaultApi";
         }
         // e.g. phone_number_api => PhoneNumberApi
diff --git a/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/RustServerCodegen.java b/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/RustServerCodegen.java
index 13f410c2d3d8..095cb333b94c 100644
--- a/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/RustServerCodegen.java
+++ b/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/RustServerCodegen.java
@@ -475,7 +475,7 @@ public CodegenOperation fromOperation(String path, String httpMethod, Operation
         //
         // Construct a Rust constant (uppercase) token name, and ensure it's
         // unique using a numeric tie-breaker if required.
-        String basePathId = sanitizeName(op.path.replace("/", "_").replace("{", "").replace("}", "").replaceAll("^_", "")).toUpperCase(Locale.ROOT);
+        String basePathId = sanitizeName(FIRST_LEADING_UNDERSCORE.matcher(op.path.replace("/", "_").replace("{", "").replace("}", "")).replaceAll("")).toUpperCase(Locale.ROOT);
         String pathId = basePathId;
         int pathIdTiebreaker = 2;
         boolean found = false;
diff --git a/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/RustServerCodegenDeprecated.java b/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/RustServerCodegenDeprecated.java
index 96f28a9b14c6..44e197a9ca2c 100644
--- a/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/RustServerCodegenDeprecated.java
+++ b/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/RustServerCodegenDeprecated.java
@@ -462,7 +462,7 @@ public CodegenOperation fromOperation(String path, String httpMethod, Operation
         //
         // Construct a Rust constant (uppercase) token name, and ensure it's
         // unique using a numeric tie-breaker if required.
-        String basePathId = sanitizeName(op.path.replace("/", "_").replace("{", "").replace("}", "").replaceAll("^_", "")).toUpperCase(Locale.ROOT);
+        String basePathId = sanitizeName(FIRST_LEADING_UNDERSCORE.matcher(op.path.replace("/", "_").replace("{", "").replace("}", "")).replaceAll("")).toUpperCase(Locale.ROOT);
         String pathId = basePathId;
         int pathIdTiebreaker = 2;
         boolean found = false;
diff --git a/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/ScalaAkkaClientCodegen.java b/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/ScalaAkkaClientCodegen.java
index 749ea34f98ef..f1608604cf23 100644
--- a/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/ScalaAkkaClientCodegen.java
+++ b/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/ScalaAkkaClientCodegen.java
@@ -305,7 +305,7 @@ public String toDefaultValue(Schema p) {
     private static class JavadocLambda extends CustomLambda {
         @Override
         public String formatFragment(String fragment) {
-            final String[] lines = fragment.split("\\r?\\n");
+            final String[] lines = DefaultCodegen.SPLIT_ON_NEWLINE.split(fragment);
             final StringBuilder sb = new StringBuilder();
             sb.append("  /**\n");
             for (String line : lines) {
diff --git a/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/ScalaCaskServerCodegen.java b/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/ScalaCaskServerCodegen.java
index 7179f7374817..0e51eee3b5ec 100644
--- a/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/ScalaCaskServerCodegen.java
+++ b/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/ScalaCaskServerCodegen.java
@@ -45,6 +45,11 @@ public class ScalaCaskServerCodegen extends AbstractScalaCodegen implements Code
     // citizen of cask
     private static final String AdditionalPropertiesType = "Value";
 
+    /** Matches any character that is not alphanumeric, underscore, ], or [. */
+    private static final Pattern NON_IDENTIFIER_CHAR = Pattern.compile("[^a-zA-Z0-9_\\]\\[]");
+    /** Matches the inner type of a collection, e.g. {@code List[Foo]} → {@code Foo}. */
+    private static final Pattern INNER_COLLECTION_TYPE = Pattern.compile(".*\\[(.*)]");
+
     private final Logger LOGGER = LoggerFactory.getLogger(ScalaCaskServerCodegen.class);
 
     @Override
@@ -323,7 +328,7 @@ public String apiInterfaceFileFolder() {
 
     static String asMethod(final String input) {
         // Remove all non-alphanumeric characters using regex
-        String alphanumeric = input.replaceAll("[^a-zA-Z0-9]", "");
+        String alphanumeric = NON_ALPHANUMERIC_CHAR.matcher(input).replaceAll("");
 
         // Ensure the method name doesn't start with a digit
         if (alphanumeric.isEmpty()) {
@@ -940,7 +945,7 @@ private void postProcessProperty(final CodegenProperty p) {
          *           type: string
          * }}}
          */
-        if (p.datatypeWithEnum != null && p.datatypeWithEnum.matches(".*[^a-zA-Z0-9_\\]\\[].*")) {
+        if (p.datatypeWithEnum != null && NON_IDENTIFIER_CHAR.matcher(p.datatypeWithEnum).find()) {
             p.datatypeWithEnum = fixBackTicks(p.datatypeWithEnum);
         }
 
@@ -1238,11 +1243,11 @@ private static String chompSuffix(String str, String suffix) {
     }
 
     private static boolean hasBrackets(String str) {
-        return str.matches("^\\{(.*)\\}$");
+        return IS_PATH_PARAM.matcher(str).matches();
     }
 
     static String containerType(String dataType) {
-        String fixedForList = dataType.replaceAll(".*\\[(.*)\\]", "$1");
+        String fixedForList = INNER_COLLECTION_TYPE.matcher(dataType).replaceAll("$1");
 
         // if it is a map, we want the value type
         final String[] parts = fixedForList.split(",");
diff --git a/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/ScalaFinchServerCodegen.java b/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/ScalaFinchServerCodegen.java
index e6144e081f92..d51074d73f40 100644
--- a/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/ScalaFinchServerCodegen.java
+++ b/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/ScalaFinchServerCodegen.java
@@ -32,6 +32,10 @@
 import java.util.*;
 
 public class ScalaFinchServerCodegen extends DefaultCodegen implements CodegenConfig {
+
+    /** Matches the non-bracket prefix of a collection type, e.g. {@code "List"} in {@code "List[String]"}. */
+    private static final java.util.regex.Pattern NON_BRACKET_PREFIX = java.util.regex.Pattern.compile("^[^\\[]+");
+
     private final Logger LOGGER = LoggerFactory.getLogger(ScalaFinchServerCodegen.class);
     protected String invokerPackage = "org.openapitools.client";
     protected String groupId = "org.openapitools";
@@ -383,7 +387,7 @@ private void generateScalaPath(CodegenOperation op) {
 
         for (String item : items) {
 
-            if (item.matches("^\\{(.*)}$")) { // wrap in {}
+            if (IS_PATH_PARAM.matcher(item).matches()) { // wrap in {}
                 // find the datatype of the parameter
                 final CodegenParameter cp = op.pathParams.get(pathParamIndex);
 
@@ -429,7 +433,7 @@ private void generateInputParameters(CodegenOperation op) {
                 p.vendorExtensions.put("x-codegen-normalized-input-type", p.dataType);
             } else if (p.isContainer || p.isArray) {
                 p.vendorExtensions.put("x-codegen-normalized-path-type", toPathParameter(p, "params", false));
-                p.vendorExtensions.put("x-codegen-normalized-input-type", p.dataType.replaceAll("^[^\\[]+", "Seq"));
+                p.vendorExtensions.put("x-codegen-normalized-input-type", NON_BRACKET_PREFIX.matcher(p.dataType).replaceAll("Seq"));
             } else if (p.isQueryParam) {
                 p.vendorExtensions.put("x-codegen-normalized-path-type", toPathParameter(p, "param", true));
                 p.vendorExtensions.put("x-codegen-normalized-input-type", toInputParameter(p));
diff --git a/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/ScalaGatlingCodegen.java b/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/ScalaGatlingCodegen.java
index 3a9eb9b1c1c7..2dfef0551e46 100644
--- a/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/ScalaGatlingCodegen.java
+++ b/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/ScalaGatlingCodegen.java
@@ -268,7 +268,7 @@ public void preprocessOpenAPI(OpenAPI openAPI) {
 
                 if (!operation.getExtensions().keySet().contains("x-gatling-path")) {
                     if (pathname.contains("{")) {
-                        String gatlingPath = pathname.replaceAll("\\{", "\\$\\{");
+                        String gatlingPath = LEFT_CURLY_BRACE.matcher(pathname).replaceAll("\\${");
                         operation.addExtension("x-gatling-path", gatlingPath);
                     } else {
                         operation.addExtension("x-gatling-path", pathname);
diff --git a/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/ScalaHttp4sServerCodegen.java b/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/ScalaHttp4sServerCodegen.java
index fe8098feb1ce..e92778fab32e 100644
--- a/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/ScalaHttp4sServerCodegen.java
+++ b/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/ScalaHttp4sServerCodegen.java
@@ -787,7 +787,7 @@ private void generateScalaPath(CodegenOperation op) {
 
         for (String item : items) {
 
-            if (item.matches("^\\{(.*)}$")) { // wrap in {}
+            if (IS_PATH_PARAM.matcher(item).matches()) { // wrap in {}
                 // find the datatype of the parameter
                 final CodegenParameter cp = op.pathParams.get(pathParamIndex);
 
diff --git a/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/ScalaLagomServerCodegen.java b/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/ScalaLagomServerCodegen.java
index 57efc5671b20..dbb5a30d004b 100644
--- a/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/ScalaLagomServerCodegen.java
+++ b/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/ScalaLagomServerCodegen.java
@@ -190,7 +190,7 @@ public ModelsMap postProcessModelsEnum(ModelsMap objs) {
 
                     for (final ListIterator<Object> i = enumValues.listIterator(); i.hasNext(); ) {
                         final String element = String.valueOf(i.next());
-                        i.set(element.replaceAll("^\"|\"$", ""));
+                        i.set(ENCLOSING_QUOTES.matcher(element).replaceAll(""));
                     }
                 }
             }
@@ -222,7 +222,7 @@ public OperationsMap postProcessOperationsWithModels(OperationsMap objs, List<Mo
 
         for (CodegenOperation codegenOperation : oplist) {
             String path = codegenOperation.path;
-            codegenOperation.path = path.replaceAll("\\{", ":").replaceAll("}", "");
+            codegenOperation.path = RIGHT_CURLY_BRACE.matcher(LEFT_CURLY_BRACE.matcher(path).replaceAll(":")).replaceAll("");
         }
         return objs;
     }
diff --git a/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/ScalaPekkoClientCodegen.java b/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/ScalaPekkoClientCodegen.java
index 1eb47d1d0f80..293680bcb3a3 100644
--- a/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/ScalaPekkoClientCodegen.java
+++ b/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/ScalaPekkoClientCodegen.java
@@ -303,7 +303,7 @@ public String toDefaultValue(Schema p) {
     private static class JavadocLambda extends CustomLambda {
         @Override
         public String formatFragment(String fragment) {
-            final String[] lines = fragment.split("\\r?\\n");
+            final String[] lines = DefaultCodegen.SPLIT_ON_NEWLINE.split(fragment);
             final StringBuilder sb = new StringBuilder();
             sb.append("  /**\n");
             for (String line : lines) {
diff --git a/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/ScalaPlayFrameworkServerCodegen.java b/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/ScalaPlayFrameworkServerCodegen.java
index 13017961c66f..9720246bc957 100644
--- a/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/ScalaPlayFrameworkServerCodegen.java
+++ b/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/ScalaPlayFrameworkServerCodegen.java
@@ -31,7 +31,6 @@
 import java.io.File;
 import java.util.*;
 import java.util.regex.Matcher;
-import java.util.regex.Pattern;
 import java.util.stream.Collectors;
 
 import static org.apache.commons.lang3.StringUtils.rightPad;
@@ -40,6 +39,7 @@
 import static org.openapitools.codegen.utils.StringUtils.camelize;
 
 public class ScalaPlayFrameworkServerCodegen extends AbstractScalaCodegen implements CodegenConfig {
+
     public static final String TITLE = "title";
     public static final String SKIP_STUBS = "skipStubs";
     public static final String SUPPORT_ASYNC = "supportAsync";
@@ -214,8 +214,7 @@ public OperationsMap postProcessOperationsWithModels(OperationsMap objs, List<Mo
         if (operations != null) {
             List<CodegenOperation> ops = operations.getOperation();
             for (CodegenOperation operation : ops) {
-                Pattern pathVariableMatcher = Pattern.compile("\\{([^}]+)}");
-                Matcher match = pathVariableMatcher.matcher(operation.path);
+                Matcher match = PATH_PARAMETER.matcher(operation.path);
                 while (match.find()) {
                     String completeMatch = match.group();
                     String replacement = ":" + camelize(match.group(1), LOWERCASE_FIRST_LETTER);
@@ -373,8 +372,8 @@ public String toEnumVarName(String value, String datatype) {
             return "EMPTY";
         }
 
-        String var = camelize(value.replaceAll("\\W+", "_"));
-        if (var.matches("\\d.*")) {
+        String var = camelize(NON_WORD_PLUS.matcher(value).replaceAll("_"));
+        if (STARTS_WITH_DIGIT.matcher(var).matches()) {
             return "_" + var;
         } else {
             return var;
diff --git a/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/ScalaSttp4ClientCodegen.java b/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/ScalaSttp4ClientCodegen.java
index b628cb615500..20ae0974ee0b 100644
--- a/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/ScalaSttp4ClientCodegen.java
+++ b/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/ScalaSttp4ClientCodegen.java
@@ -585,7 +585,7 @@ public String getInvokerPackage(Map<String, Object> additionalProperties) {
     private static class JavadocLambda extends CustomLambda {
         @Override
         public String formatFragment(String fragment) {
-            final String[] lines = fragment.split("\\r?\\n");
+            final String[] lines = DefaultCodegen.SPLIT_ON_NEWLINE.split(fragment);
             final StringBuilder sb = new StringBuilder();
             sb.append("  /**\n");
             for (String line : lines) {
diff --git a/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/ScalaSttp4JsoniterClientCodegen.java b/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/ScalaSttp4JsoniterClientCodegen.java
index c47a7a390680..94fd2cb535cb 100644
--- a/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/ScalaSttp4JsoniterClientCodegen.java
+++ b/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/ScalaSttp4JsoniterClientCodegen.java
@@ -670,7 +670,7 @@ public String getInvokerPackage(Map<String, Object> additionalProperties) {
     private static class JavadocLambda extends CustomLambda {
         @Override
         public String formatFragment(String fragment) {
-            final String[] lines = fragment.split("\\r?\\n");
+            final String[] lines = DefaultCodegen.SPLIT_ON_NEWLINE.split(fragment);
             final StringBuilder sb = new StringBuilder();
             sb.append("  /**\n");
             for (String line : lines) {
diff --git a/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/ScalaSttpClientCodegen.java b/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/ScalaSttpClientCodegen.java
index f4aa0e66327d..ac1f0acae9e5 100644
--- a/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/ScalaSttpClientCodegen.java
+++ b/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/ScalaSttpClientCodegen.java
@@ -585,7 +585,7 @@ public String getInvokerPackage(Map<String, Object> additionalProperties) {
     private static class JavadocLambda extends CustomLambda {
         @Override
         public String formatFragment(String fragment) {
-            final String[] lines = fragment.split("\\r?\\n");
+            final String[] lines = DefaultCodegen.SPLIT_ON_NEWLINE.split(fragment);
             final StringBuilder sb = new StringBuilder();
             sb.append("  /**\n");
             for (String line : lines) {
diff --git a/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/Swift5ClientCodegen.java b/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/Swift5ClientCodegen.java
index 57ee37e1221b..ab15dd6a6ab6 100644
--- a/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/Swift5ClientCodegen.java
+++ b/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/Swift5ClientCodegen.java
@@ -768,7 +768,7 @@ public String toModelName(String name) {
         }
 
         // model name starts with number
-        if (name.matches("^\\d.*")) {
+        if (STARTS_WITH_DIGIT.matcher(name).matches()) {
             // e.g. 200Response => Model200Response (after camelize)
             String modelName = "Model" + name;
             LOGGER.warn("{} (model name starts with number) cannot be used as model name. Renamed to {}", name,
@@ -872,7 +872,7 @@ public String toOperationId(String operationId) {
         }
 
         // operationId starts with a number
-        if (operationId.matches("^\\d.*")) {
+        if (STARTS_WITH_DIGIT.matcher(operationId).matches()) {
             LOGGER.warn("{} (starting with a number) cannot be used as method name. Renamed to {}", operationId, camelize(sanitizeName("call_" + operationId), LOWERCASE_FIRST_LETTER));
             operationId = camelize(sanitizeName("call_" + operationId), LOWERCASE_FIRST_LETTER);
         }
@@ -891,7 +891,7 @@ public String toVarName(String name) {
         name = sanitizeName(name);
 
         // if it's all upper case, do nothing
-        if (name.matches("^[A-Z_]*$")) {
+        if (ALL_UPPER_UNDERSCORE.matcher(name).matches()) {
             return name;
         }
 
@@ -905,7 +905,7 @@ public String toVarName(String name) {
         }
 
         // for words starting with number, append _
-        if (name.matches("^\\d.*")) {
+        if (STARTS_WITH_DIGIT.matcher(name).matches()) {
             name = "_" + name;
         }
 
@@ -923,10 +923,10 @@ public String toParamName(String name) {
         name = sanitizeName(name);
 
         // replace - with _ e.g. created-at => created_at
-        name = name.replaceAll("-", "_");
+        name = MINUS.matcher(name).replaceAll("_");
 
         // if it's all upper case, do nothing
-        if (name.matches("^[A-Z_]*$")) {
+        if (ALL_UPPER_UNDERSCORE.matcher(name).matches()) {
             return name;
         }
 
@@ -940,7 +940,7 @@ public String toParamName(String name) {
         }
 
         // for words starting with number, append _
-        if (name.matches("^\\d.*")) {
+        if (STARTS_WITH_DIGIT.matcher(name).matches()) {
             name = "_" + name;
         }
 
@@ -1021,7 +1021,7 @@ public String toEnumVarName(String name, String datatype) {
         }
 
         // Prefix with underscore if name starts with number
-        if (name.matches("\\d.*")) {
+        if (STARTS_WITH_DIGIT.matcher(name).matches()) {
             return "_" + replaceSpecialCharacters(camelize(name, LOWERCASE_FIRST_LETTER));
         }
 
@@ -1032,7 +1032,7 @@ public String toEnumVarName(String name, String datatype) {
 
         // Camelize only when we have a structure defined below
         boolean camelized = false;
-        if (name.matches("[A-Z][a-z0-9]+[a-zA-Z0-9]*")) {
+        if (CAMEL_INITIAL.matcher(name).matches()) {
             name = camelize(name, LOWERCASE_FIRST_LETTER);
             camelized = true;
         }
@@ -1051,8 +1051,8 @@ public String toEnumVarName(String name, String datatype) {
         }
 
         char[] separators = {'-', '_', ' ', ':', '(', ')'};
-        return camelize(replaceSpecialCharacters(WordUtils.capitalizeFully(StringUtils.lowerCase(name), separators)
-                        .replaceAll("[-_ :\\(\\)]", "")),
+        return camelize(replaceSpecialCharacters(DASH_UNDERSCORE_SPACE_COLON_PARENTHESES.matcher(WordUtils.capitalizeFully(StringUtils.lowerCase(name), separators))
+                        .replaceAll("")),
                 LOWERCASE_FIRST_LETTER);
     }
 
@@ -1071,7 +1071,7 @@ private String replaceSpecialCharacters(String name) {
         }
 
         // Fallback, replace unknowns with underscore.
-        name = name.replaceAll("\\W+", "_");
+        name = NON_WORD_PLUS.matcher(name).replaceAll("_");
 
         return name;
     }
@@ -1120,7 +1120,7 @@ public String toEnumName(CodegenProperty property) {
 
         // TODO: toModelName already does something for names starting with number,
         // so this code is probably never called
-        if (enumName.matches("\\d.*")) { // starts with number
+        if (STARTS_WITH_DIGIT.matcher(enumName).matches()) { // starts with number
             return "_" + enumName;
         } else {
             return enumName;
diff --git a/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/Swift6ClientCodegen.java b/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/Swift6ClientCodegen.java
index caec04adb227..7027918f56a7 100644
--- a/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/Swift6ClientCodegen.java
+++ b/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/Swift6ClientCodegen.java
@@ -811,7 +811,7 @@ public String toModelName(String name) {
         }
 
         // model name starts with number
-        if (name.matches("^\\d.*")) {
+        if (STARTS_WITH_DIGIT.matcher(name).matches()) {
             // e.g. 200Response => Model200Response (after camelize)
             String modelName = "Model" + name;
             LOGGER.warn("{} (model name starts with number) cannot be used as model name. Renamed to {}", name,
@@ -915,7 +915,7 @@ public String toOperationId(String operationId) {
         }
 
         // operationId starts with a number
-        if (operationId.matches("^\\d.*")) {
+        if (STARTS_WITH_DIGIT.matcher(operationId).matches()) {
             LOGGER.warn("{} (starting with a number) cannot be used as method name. Renamed to {}", operationId, camelize(sanitizeName("call_" + operationId), LOWERCASE_FIRST_LETTER));
             operationId = camelize(sanitizeName("call_" + operationId), LOWERCASE_FIRST_LETTER);
         }
@@ -934,7 +934,7 @@ public String toVarName(String name) {
         name = sanitizeName(name);
 
         // if it's all upper case, do nothing
-        if (name.matches("^[A-Z_]*$")) {
+        if (ALL_UPPER_UNDERSCORE.matcher(name).matches()) {
             return name;
         }
 
@@ -948,7 +948,7 @@ public String toVarName(String name) {
         }
 
         // for words starting with number, append _
-        if (name.matches("^\\d.*")) {
+        if (STARTS_WITH_DIGIT.matcher(name).matches()) {
             name = "_" + name;
         }
 
@@ -966,10 +966,10 @@ public String toParamName(String name) {
         name = sanitizeName(name);
 
         // replace - with _ e.g. created-at => created_at
-        name = name.replaceAll("-", "_");
+        name = MINUS.matcher(name).replaceAll("_");
 
         // if it's all upper case, do nothing
-        if (name.matches("^[A-Z_]*$")) {
+        if (ALL_UPPER_UNDERSCORE.matcher(name).matches()) {
             return name;
         }
 
@@ -983,7 +983,7 @@ public String toParamName(String name) {
         }
 
         // for words starting with number, append _
-        if (name.matches("^\\d.*")) {
+        if (STARTS_WITH_DIGIT.matcher(name).matches()) {
             name = "_" + name;
         }
 
@@ -1064,7 +1064,7 @@ public String toEnumVarName(String name, String datatype) {
         }
 
         // Prefix with underscore if name starts with number
-        if (name.matches("\\d.*")) {
+        if (STARTS_WITH_DIGIT.matcher(name).matches()) {
             return "_" + replaceSpecialCharacters(camelize(name, LOWERCASE_FIRST_LETTER));
         }
 
@@ -1075,7 +1075,7 @@ public String toEnumVarName(String name, String datatype) {
 
         // Camelize only when we have a structure defined below
         boolean camelized = false;
-        if (name.matches("[A-Z][a-z0-9]+[a-zA-Z0-9]*")) {
+        if (CAMEL_INITIAL.matcher(name).matches()) {
             name = camelize(name, LOWERCASE_FIRST_LETTER);
             camelized = true;
         }
@@ -1094,8 +1094,8 @@ public String toEnumVarName(String name, String datatype) {
         }
 
         char[] separators = {'-', '_', ' ', ':', '(', ')'};
-        return camelize(replaceSpecialCharacters(WordUtils.capitalizeFully(StringUtils.lowerCase(name), separators)
-                        .replaceAll("[-_ :\\(\\)]", "")),
+        return camelize(replaceSpecialCharacters(DASH_UNDERSCORE_SPACE_COLON_PARENTHESES.matcher(WordUtils.capitalizeFully(StringUtils.lowerCase(name), separators))
+                        .replaceAll("")),
                 LOWERCASE_FIRST_LETTER);
     }
 
@@ -1125,7 +1125,7 @@ private String replaceSpecialCharacters(String name) {
         }
 
         // Fallback, replace unknowns with underscore.
-        name = name.replaceAll("\\W+", "_");
+        name = NON_WORD_PLUS.matcher(name).replaceAll("_");
 
         return name;
     }
@@ -1174,7 +1174,7 @@ public String toEnumName(CodegenProperty property) {
 
         // TODO: toModelName already does something for names starting with number,
         // so this code is probably never called
-        if (enumName.matches("\\d.*")) { // starts with number
+        if (STARTS_WITH_DIGIT.matcher(enumName).matches()) { // starts with number
             return "_" + enumName;
         } else {
             return enumName;
diff --git a/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/SwiftCombineClientCodegen.java b/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/SwiftCombineClientCodegen.java
index d321fd0d856d..9ef3aef332b0 100644
--- a/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/SwiftCombineClientCodegen.java
+++ b/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/SwiftCombineClientCodegen.java
@@ -51,6 +51,9 @@
 public class SwiftCombineClientCodegen extends DefaultCodegen implements CodegenConfig {
     private final Logger LOGGER = LoggerFactory.getLogger(SwiftCombineClientCodegen.class);
 
+    /** Matches a Swift identifier starting with an uppercase letter followed by lowercase+digits. */
+    // CAMEL_INITIAL pattern is inherited from DefaultCodegen
+
     public static final String PROJECT_NAME = "projectName";
     public static final String MAP_FILE_BINARY_TO_DATA = "mapFileBinaryToData";
     @Setter protected String projectName = "OpenAPIClient";
@@ -369,7 +372,7 @@ public String toModelName(String name) {
         }
 
         // model name starts with number
-        if (name.matches("^\\d.*")) {
+        if (STARTS_WITH_DIGIT.matcher(name).matches()) {
             // e.g. 200Response => Model200Response (after camelize)
             String modelName = "Model" + name;
             LOGGER.warn("{} (model name starts with number) cannot be used as model name. Renamed to {}", name,
@@ -465,7 +468,7 @@ public String toOperationId(String operationId) {
         }
 
         // operationId starts with a number
-        if (operationId.matches("^\\d.*")) {
+        if (STARTS_WITH_DIGIT.matcher(operationId).matches()) {
             LOGGER.warn("{} (starting with a number) cannot be used as method name. Renamed to {}", operationId, camelize(sanitizeName("call_" + operationId), LOWERCASE_FIRST_LETTER));
             operationId = camelize(sanitizeName("call_" + operationId), LOWERCASE_FIRST_LETTER);
         }
@@ -480,7 +483,7 @@ public String toVarName(String name) {
         name = sanitizeName(name);
 
         // if it's all upper case, do nothing
-        if (name.matches("^[A-Z_]*$")) {
+        if (ALL_UPPER_UNDERSCORE.matcher(name).matches()) {
             return name;
         }
 
@@ -494,7 +497,7 @@ public String toVarName(String name) {
         }
 
         // for words starting with number, append _
-        if (name.matches("^\\d.*")) {
+        if (STARTS_WITH_DIGIT.matcher(name).matches()) {
             name = "_" + name;
         }
 
@@ -507,10 +510,10 @@ public String toParamName(String name) {
         name = sanitizeName(name);
 
         // replace - with _ e.g. created-at => created_at
-        name = name.replaceAll("-", "_");
+        name = MINUS.matcher(name).replaceAll("_");
 
         // if it's all upper case, do nothing
-        if (name.matches("^[A-Z_]*$")) {
+        if (ALL_UPPER_UNDERSCORE.matcher(name).matches()) {
             return name;
         }
 
@@ -524,7 +527,7 @@ public String toParamName(String name) {
         }
 
         // for words starting with number, append _
-        if (name.matches("^\\d.*")) {
+        if (STARTS_WITH_DIGIT.matcher(name).matches()) {
             name = "_" + name;
         }
 
@@ -595,7 +598,7 @@ public String toEnumVarName(String name, String datatype) {
 
         // Camelize only when we have a structure defined below
         Boolean camelized = false;
-        if (name.matches("[A-Z][a-z0-9]+[a-zA-Z0-9]*")) {
+        if (CAMEL_INITIAL.matcher(name).matches()) {
             name = camelize(name, LOWERCASE_FIRST_LETTER);
             camelized = true;
         }
@@ -610,9 +613,9 @@ public String toEnumVarName(String name, String datatype) {
         if ("Int".equals(datatype) || "Int32".equals(datatype) || "Int64".equals(datatype)
                 || "Float".equals(datatype) || "Double".equals(datatype)) {
             String varName = "number" + camelize(name);
-            varName = varName.replaceAll("-", "minus");
-            varName = varName.replaceAll("\\+", "plus");
-            varName = varName.replaceAll("\\.", "dot");
+            varName = MINUS.matcher(varName).replaceAll("minus");
+            varName = PLUS.matcher(varName).replaceAll("plus");
+            varName = DOT.matcher(varName).replaceAll("dot");
             return varName;
         }
 
@@ -623,8 +626,8 @@ public String toEnumVarName(String name, String datatype) {
         }
 
         char[] separators = {'-', '_', ' ', ':', '(', ')'};
-        return camelize(WordUtils.capitalizeFully(StringUtils.lowerCase(name), separators)
-                        .replaceAll("[-_ :\\(\\)]", ""),
+        return camelize(DASH_UNDERSCORE_SPACE_COLON_PARENTHESES.matcher(WordUtils.capitalizeFully(StringUtils.lowerCase(name), separators))
+                        .replaceAll(""),
                 LOWERCASE_FIRST_LETTER);
     }
 
@@ -646,7 +649,7 @@ public String toEnumName(CodegenProperty property) {
 
         // TODO: toModelName already does something for names starting with number,
         // so this code is probably never called
-        if (enumName.matches("\\d.*")) { // starts with number
+        if (STARTS_WITH_DIGIT.matcher(enumName).matches()) { // starts with number
             return "_" + enumName;
         } else {
             return enumName;
diff --git a/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/TerraformProviderCodegen.java b/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/TerraformProviderCodegen.java
index 7cc6bcfbcf98..4b51a7e97056 100644
--- a/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/TerraformProviderCodegen.java
+++ b/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/TerraformProviderCodegen.java
@@ -24,11 +24,13 @@
 import org.openapitools.codegen.model.ModelsMap;
 import org.openapitools.codegen.model.OperationMap;
 import org.openapitools.codegen.model.OperationsMap;
+import org.openapitools.codegen.utils.PatternCache;
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
 
 import java.io.File;
 import java.util.*;
+import java.util.regex.Pattern;
 
 import static org.openapitools.codegen.utils.StringUtils.camelize;
 import static org.openapitools.codegen.utils.StringUtils.underscore;
@@ -37,6 +39,9 @@ public class TerraformProviderCodegen extends AbstractGoCodegen {
 
     private final Logger LOGGER = LoggerFactory.getLogger(TerraformProviderCodegen.class);
 
+    /** Case-insensitive match of a trailing "api" suffix. */
+    private static final Pattern API_SUFFIX = Pattern.compile("(?i)api$");
+
     public static final String PROVIDER_NAME = "providerName";
     public static final String PROVIDER_ADDRESS = "providerAddress";
     public static final String PROVIDER_VERSION = "providerVersion";
@@ -296,7 +301,7 @@ public OperationsMap postProcessOperationsWithModels(OperationsMap objs, List<Mo
         // Determine resource name from tag
         String tag = objectMap.getClassname();
         // Strip common suffixes like "Api", "API" from the tag name
-        String cleanTag = tag.replaceAll("(?i)api$", "");
+        String cleanTag = API_SUFFIX.matcher(tag).replaceAll("");
         if (cleanTag.isEmpty()) {
             cleanTag = tag;
         }
@@ -389,7 +394,7 @@ public OperationsMap postProcessOperationsWithModels(OperationsMap objs, List<Mo
                     }
                     // Try stripping resource name prefix (e.g., petId -> id)
                     if (!idResolved) {
-                        String strippedId = idField.replaceFirst("(?i)^" + resourceName, "");
+                        String strippedId = PatternCache.get("(?i)^" + java.util.regex.Pattern.quote(resourceName)).matcher(idField).replaceFirst("");
                         if (!strippedId.isEmpty()) {
                             for (CodegenProperty prop : model.vars) {
                                 if (prop.baseName.equalsIgnoreCase(strippedId)) {
diff --git a/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/TypeScriptAngularClientCodegen.java b/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/TypeScriptAngularClientCodegen.java
index 8190aa46c700..587409afcc73 100644
--- a/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/TypeScriptAngularClientCodegen.java
+++ b/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/TypeScriptAngularClientCodegen.java
@@ -48,9 +48,9 @@
 public class TypeScriptAngularClientCodegen extends AbstractTypeScriptClientCodegen {
     private final Logger LOGGER = LoggerFactory.getLogger(TypeScriptAngularClientCodegen.class);
 
-    private static String CLASS_NAME_PREFIX_PATTERN = "^[a-zA-Z0-9]*$";
-    private static String CLASS_NAME_SUFFIX_PATTERN = "^[a-zA-Z0-9]*$";
-    private static String FILE_NAME_SUFFIX_PATTERN = "^[a-zA-Z0-9.-]*$";
+    private static final java.util.regex.Pattern CLASS_NAME_PREFIX_PATTERN = java.util.regex.Pattern.compile("^[a-zA-Z0-9]*$");
+    private static final java.util.regex.Pattern CLASS_NAME_SUFFIX_PATTERN = java.util.regex.Pattern.compile("^[a-zA-Z0-9]*$");
+    private static final java.util.regex.Pattern FILE_NAME_SUFFIX_PATTERN  = java.util.regex.Pattern.compile("^[a-zA-Z0-9.-]*$");
 
     public static enum QUERY_PARAM_OBJECT_FORMAT_TYPE {dot, json, key}
 
@@ -657,7 +657,7 @@ public String removeModelPrefixSuffix(String name) {
      * @param value    The value that is being validated.
      */
     private void validateFileSuffixArgument(String argument, String value) {
-        if (!value.matches(FILE_NAME_SUFFIX_PATTERN)) {
+        if (!FILE_NAME_SUFFIX_PATTERN.matcher(value).matches()) {
             throw new IllegalArgumentException(
                     String.format(Locale.ROOT, "%s file suffix only allows '.', '-' and alphanumeric characters.", argument)
             );
@@ -672,7 +672,7 @@ private void validateFileSuffixArgument(String argument, String value) {
      * @param value    The value that is being validated.
      */
     private void validateClassPrefixArgument(String argument, String value) {
-        if (!value.matches(CLASS_NAME_PREFIX_PATTERN)) {
+        if (!CLASS_NAME_PREFIX_PATTERN.matcher(value).matches()) {
             throw new IllegalArgumentException(
                     String.format(Locale.ROOT, "%s class prefix only allows alphanumeric characters.", argument)
             );
@@ -687,7 +687,7 @@ private void validateClassPrefixArgument(String argument, String value) {
      * @param value    The value that is being validated.
      */
     private void validateClassSuffixArgument(String argument, String value) {
-        if (!value.matches(CLASS_NAME_SUFFIX_PATTERN)) {
+        if (!CLASS_NAME_SUFFIX_PATTERN.matcher(value).matches()) {
             throw new IllegalArgumentException(
                     String.format(Locale.ROOT, "%s class suffix only allows alphanumeric characters.", argument)
             );
diff --git a/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/TypeScriptAxiosClientCodegen.java b/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/TypeScriptAxiosClientCodegen.java
index 6898d3d7ccfd..e61571a7be12 100644
--- a/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/TypeScriptAxiosClientCodegen.java
+++ b/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/TypeScriptAxiosClientCodegen.java
@@ -127,8 +127,8 @@ private static String getRelativeToRoot(String path) {
     @Override
     public void processOpts() {
         super.processOpts();
-        tsModelPackage = modelPackage.replaceAll("\\.", "/");
-        String tsApiPackage = apiPackage.replaceAll("\\.", "/");
+        tsModelPackage = DOT.matcher(modelPackage).replaceAll("/");
+        String tsApiPackage = DOT.matcher(apiPackage).replaceAll("/");
 
         String modelRelativeToRoot = getRelativeToRoot(tsModelPackage);
         String apiRelativeToRoot = getRelativeToRoot(tsApiPackage);
@@ -270,7 +270,7 @@ public ModelsMap postProcessModels(ModelsMap objs) {
             }
 
             // Deduce the model file name in kebab case
-            cm.classFilename = cm.classname.replaceAll("([a-z0-9])([A-Z])", "$1-$2").toLowerCase(Locale.ROOT);
+            cm.classFilename = CAMEL_CASE_BOUNDARY.matcher(cm.classname).replaceAll("$1-$2").toLowerCase(Locale.ROOT);
 
             //processed enum names
             if (!withoutPrefixEnums) {
@@ -299,7 +299,7 @@ public ModelsMap postProcessModels(ModelsMap objs) {
             String tsImport = tsModelPackage + "/" + javaImport;
             m.put("tsImport", tsImport);
             m.put("class", javaImport);
-            m.put("filename", javaImport.replaceAll("([a-z0-9])([A-Z])", "$1-$2").toLowerCase(Locale.ROOT));
+            m.put("filename", CAMEL_CASE_BOUNDARY.matcher(javaImport).replaceAll("$1-$2").toLowerCase(Locale.ROOT));
         }
         return objs;
     }
@@ -329,12 +329,12 @@ public String toRegularExpression(String pattern) {
 
     @Override
     public String toModelFilename(String name) {
-        return super.toModelFilename(name).replaceAll("([a-z0-9])([A-Z])", "$1-$2").toLowerCase(Locale.ROOT);
+        return CAMEL_CASE_BOUNDARY.matcher(super.toModelFilename(name)).replaceAll("$1-$2").toLowerCase(Locale.ROOT);
     }
 
     @Override
     public String toApiFilename(String name) {
-        return super.toApiFilename(name).replaceAll("([a-z0-9])([A-Z])", "$1-$2").toLowerCase(Locale.ROOT);
+        return CAMEL_CASE_BOUNDARY.matcher(super.toApiFilename(name)).replaceAll("$1-$2").toLowerCase(Locale.ROOT);
     }
 
     private void addNpmPackageGeneration() {
diff --git a/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/TypeScriptClientCodegen.java b/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/TypeScriptClientCodegen.java
index 085461f446ea..8e8a4aba88b8 100644
--- a/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/TypeScriptClientCodegen.java
+++ b/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/TypeScriptClientCodegen.java
@@ -49,7 +49,6 @@
 import java.time.format.DateTimeFormatter;
 import java.util.*;
 import java.util.regex.Matcher;
-import java.util.regex.Pattern;
 
 import static org.openapitools.codegen.utils.CamelizeOption.LOWERCASE_FIRST_LETTER;
 import static org.openapitools.codegen.utils.OnceLogger.once;
@@ -60,6 +59,9 @@
 public class TypeScriptClientCodegen extends AbstractTypeScriptClientCodegen implements CodegenConfig {
     private final Logger LOGGER = LoggerFactory.getLogger(TypeScriptClientCodegen.class);
 
+    /** Splits a TypeScript composed-type string on {@code |}, {@code &}, {@code <}, or {@code >}. */
+    private static final java.util.regex.Pattern COMPOSED_TYPE_DELIMITERS = java.util.regex.Pattern.compile("[|&<>]");
+
     private static final String FRAMEWORK_SWITCH = "framework";
     private static final String FRAMEWORK_SWITCH_DESC = "Specify the framework which should be used in the client code.";
     private static final String[] FRAMEWORKS = {"fetch-api", "jquery"};
@@ -262,7 +264,7 @@ public String toParamName(String name) {
         }
 
         // if it's all upper case, do nothing
-        if (name.matches("^[A-Z_]*$")) {
+        if (ALL_UPPER_UNDERSCORE.matcher(name).matches()) {
             return name;
         }
 
@@ -279,7 +281,7 @@ public String toVarName(String name) {
         }
 
         // if it's all upper case, do nothing
-        if (name.matches("^[A-Z_]*$")) {
+        if (ALL_UPPER_UNDERSCORE.matcher(name).matches()) {
             return name;
         }
 
@@ -316,20 +318,20 @@ public String toEnumVarName(String name, String datatype) {
         if ("number".equals(datatype)) {
             String varName = "NUMBER_" + name;
 
-            varName = varName.replaceAll("-", "MINUS_");
-            varName = varName.replaceAll("\\+", "PLUS_");
-            varName = varName.replaceAll("\\.", "_DOT_");
+            varName = MINUS.matcher(varName).replaceAll("MINUS_");
+            varName = PLUS.matcher(varName).replaceAll("PLUS_");
+            varName = DOT.matcher(varName).replaceAll("_DOT_");
             return varName;
         }
 
         // string
         String enumName = sanitizeName(name);
-        enumName = enumName.replaceFirst("^_", "");
-        enumName = enumName.replaceFirst("_$", "");
+        enumName = FIRST_LEADING_UNDERSCORE.matcher(enumName).replaceFirst("");
+        enumName = LAST_TRAILING_UNDERSCORE.matcher(enumName).replaceFirst("");
 
         enumName = getNameWithEnumPropertyNaming(enumName);
 
-        if (enumName.matches("\\d.*")) { // starts with number
+        if (STARTS_WITH_DIGIT.matcher(enumName).matches()) { // starts with number
             return "_" + enumName;
         }
 
@@ -614,8 +616,7 @@ protected Object getObjectExample(Schema sc) {
      * @return quoted string
      */
     private String ensureQuotes(String in) {
-        Pattern pattern = Pattern.compile("\r\n|\r|\n");
-        Matcher matcher = pattern.matcher(in);
+        Matcher matcher = MULTILINE_STRING.matcher(in);
         if (matcher.find()) {
             // if a string has a new line in it add backticks to make it a typescript multiline string
             return "`" + in + "`";
@@ -1133,6 +1134,6 @@ protected void addImport(Set<String> importsToBeAddedTo, String type) {
      * @return list of types
      */
     protected String[] splitComposedTypes(String type) {
-        return type.replace(" ", "").split("[|&<>]");
+        return COMPOSED_TYPE_DELIMITERS.split(type.replace(" ", ""));
     }
 }
diff --git a/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/TypeScriptFetchClientCodegen.java b/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/TypeScriptFetchClientCodegen.java
index e66f40d55342..3375dbf2dd6f 100644
--- a/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/TypeScriptFetchClientCodegen.java
+++ b/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/TypeScriptFetchClientCodegen.java
@@ -215,11 +215,11 @@ public void setSagasAndRecords(Boolean sagasAndRecords) {
     }
 
     public String getPassthroughSuffix() {
-        return detectPassthroughModelsWithSuffixAndField != null ? detectPassthroughModelsWithSuffixAndField.split("\\.")[0] : null;
+        return detectPassthroughModelsWithSuffixAndField != null ? DOT.split(detectPassthroughModelsWithSuffixAndField)[0] : null;
     }
 
     public String getPassthroughField() {
-        return detectPassthroughModelsWithSuffixAndField != null ? detectPassthroughModelsWithSuffixAndField.split("\\.")[1] : null;
+        return detectPassthroughModelsWithSuffixAndField != null ? DOT.split(detectPassthroughModelsWithSuffixAndField)[1] : null;
     }
 
     public boolean getInferUniqueIdFromNameSuffix() {
diff --git a/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/TypeScriptNestjsClientCodegen.java b/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/TypeScriptNestjsClientCodegen.java
index cfd075645e4c..854e702f7a72 100644
--- a/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/TypeScriptNestjsClientCodegen.java
+++ b/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/TypeScriptNestjsClientCodegen.java
@@ -41,8 +41,8 @@
 public class TypeScriptNestjsClientCodegen extends AbstractTypeScriptClientCodegen {
     private final Logger LOGGER = LoggerFactory.getLogger(TypeScriptNestjsClientCodegen.class);
 
-    private static String CLASS_NAME_SUFFIX_PATTERN = "^[a-zA-Z0-9]*$";
-    private static String FILE_NAME_SUFFIX_PATTERN = "^[a-zA-Z0-9.-]*$";
+    private static final java.util.regex.Pattern CLASS_NAME_SUFFIX_PATTERN = java.util.regex.Pattern.compile("^[a-zA-Z0-9]*$");
+    private static final java.util.regex.Pattern FILE_NAME_SUFFIX_PATTERN  = java.util.regex.Pattern.compile("^[a-zA-Z0-9.-]*$");
 
     public static final String NPM_REPOSITORY = "npmRepository";
     public static final String WITH_INTERFACES = "withInterfaces";
@@ -496,7 +496,7 @@ public String removeModelPrefixSuffix(String name) {
      * @param value    The value that is being validated.
      */
     private void validateFileSuffixArgument(String argument, String value) {
-        if (!value.matches(FILE_NAME_SUFFIX_PATTERN)) {
+        if (!FILE_NAME_SUFFIX_PATTERN.matcher(value).matches()) {
             throw new IllegalArgumentException(
                     String.format(Locale.ROOT, "%s file suffix only allows '.', '-' and alphanumeric characters.", argument)
             );
@@ -511,7 +511,7 @@ private void validateFileSuffixArgument(String argument, String value) {
      * @param value    The value that is being validated.
      */
     private void validateClassSuffixArgument(String argument, String value) {
-        if (!value.matches(CLASS_NAME_SUFFIX_PATTERN)) {
+        if (!CLASS_NAME_SUFFIX_PATTERN.matcher(value).matches()) {
             throw new IllegalArgumentException(
                     String.format(Locale.ROOT, "%s class suffix only allows alphanumeric characters.", argument)
             );
diff --git a/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/TypeScriptNestjsServerCodegen.java b/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/TypeScriptNestjsServerCodegen.java
index 8e8a9a2fdc1d..7e9fa789d005 100644
--- a/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/TypeScriptNestjsServerCodegen.java
+++ b/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/TypeScriptNestjsServerCodegen.java
@@ -42,8 +42,9 @@
 public class TypeScriptNestjsServerCodegen extends AbstractTypeScriptClientCodegen {
     private final Logger LOGGER = LoggerFactory.getLogger(TypeScriptNestjsServerCodegen.class);
 
-    private static String CLASS_NAME_SUFFIX_PATTERN = "^[a-zA-Z0-9]*$";
-    private static String FILE_NAME_SUFFIX_PATTERN = "^[a-zA-Z0-9.-]*$";
+    private static final java.util.regex.Pattern CLASS_NAME_SUFFIX_PATTERN = java.util.regex.Pattern.compile("^[a-zA-Z0-9]*$");
+    private static final java.util.regex.Pattern FILE_NAME_SUFFIX_PATTERN  = java.util.regex.Pattern.compile("^[a-zA-Z0-9.-]*$");
+    private static final java.util.regex.Pattern QUOTED_STRING             = java.util.regex.Pattern.compile("([\"'].*[\"'])");
 
     public static final String NPM_REPOSITORY = "npmRepository";
     public static final String TAGGED_UNIONS = "taggedUnions";
@@ -291,7 +292,7 @@ private boolean isLanguagePrimitive(String type) {
     private boolean isInlineUnion(String type) {
         return Arrays.stream(type.split("\\|"))
                 .map(String::trim)
-                .allMatch(value -> value.matches("([\"'].*[\"'])"));
+                .allMatch(value -> QUOTED_STRING.matcher(value).matches());
     }
 
     private boolean isLanguageGenericType(String type) {
@@ -322,7 +323,7 @@ public OperationsMap postProcessOperationsWithModels(OperationsMap operations, L
         List<CodegenOperation> operationList = objectMap.getOperation();
 
         for (CodegenOperation operation : operationList) {
-            operation.path = operation.path.replaceAll("\\{([^}]+)}", ":$1");
+            operation.path = PATH_PARAMETER.matcher(operation.path).replaceAll(":$1");
             operation.httpMethod = camelize(operation.httpMethod.toLowerCase(Locale.ROOT));
 
             List<CodegenParameter> params = operation.allParams;
@@ -561,7 +562,7 @@ public String removeModelPrefixSuffix(String name) {
      * @param value    The value that is being validated.
      */
     private void validateFileSuffixArgument(String argument, String value) {
-        if (value != null && !value.matches(FILE_NAME_SUFFIX_PATTERN)) {
+        if (value != null && !FILE_NAME_SUFFIX_PATTERN.matcher(value).matches()) {
             throw new IllegalArgumentException(
                     String.format(Locale.ROOT, "%s file suffix only allows '.', '-' and alphanumeric characters.", argument)
             );
@@ -576,7 +577,7 @@ private void validateFileSuffixArgument(String argument, String value) {
      * @param value    The value that is being validated.
      */
     private void validateClassSuffixArgument(String argument, String value) {
-        if (value != null && !value.matches(CLASS_NAME_SUFFIX_PATTERN)) {
+        if (value != null && !CLASS_NAME_SUFFIX_PATTERN.matcher(value).matches()) {
             throw new IllegalArgumentException(
                     String.format(Locale.ROOT, "%s class suffix only allows alphanumeric characters.", argument)
             );
diff --git a/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/WsdlSchemaCodegen.java b/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/WsdlSchemaCodegen.java
index ae4400a5acdb..18f360b3a9ac 100644
--- a/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/WsdlSchemaCodegen.java
+++ b/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/WsdlSchemaCodegen.java
@@ -25,6 +25,7 @@
 import org.openapitools.codegen.model.ModelMap;
 import org.openapitools.codegen.model.ModelsMap;
 import org.openapitools.codegen.model.OperationsMap;
+import org.openapitools.codegen.utils.PatternCache;
 
 import java.io.File;
 import java.text.Normalizer;
@@ -107,14 +108,14 @@ public void processOpts() {
 
     private String escapeTitle(String title) {
         // strip umlauts etc.
-        final String normalizedTitle = Normalizer.normalize(title, Normalizer.Form.NFD)
-                .replaceAll("[^\\p{ASCII}]", "");
+        final String normalizedTitle = PatternCache.get("[^\\p{ASCII}]").matcher(Normalizer.normalize(title, Normalizer.Form.NFD))
+                .replaceAll("");
         return super.escapeUnsafeCharacters(normalizedTitle);
     }
 
     public String processOpenapiSpecDescription(String description) {
         if (description != null) {
-            return description.replaceAll("\\s+", " ");
+            return WHITESPACE.matcher(description).replaceAll(" ");
         } else {
             return "No description provided";
         }
diff --git a/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/XojoClientCodegen.java b/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/XojoClientCodegen.java
index 2a057ce0ef40..532859bd85d6 100644
--- a/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/XojoClientCodegen.java
+++ b/modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/XojoClientCodegen.java
@@ -432,7 +432,7 @@ public String toOperationId(String operationId) {
         }
 
         // operationId starts with a number
-        if (operationId.matches("^\\d.*")) {
+        if (STARTS_WITH_DIGIT.matcher(operationId).matches()) {
             LOGGER.warn("{} (starting with a number) cannot be used as method name. Renamed to {}", operationId, camelize(sanitizeName("call_" + operationId), LOWERCASE_FIRST_LETTER));
             operationId = camelize(sanitizeName("Call_" + operationId));
         }
@@ -476,7 +476,7 @@ public String toEnumVarName(String name, String datatype) {
 
         // Camelize only when we have a structure defined below
         boolean camelized = false;
-        if (name.matches("[A-Z][a-z0-9]+[a-zA-Z0-9]*")) {
+        if (CAMEL_INITIAL.matcher(name).matches()) {
             name = camelize(name);
             camelized = true;
         }
@@ -495,8 +495,8 @@ public String toEnumVarName(String name, String datatype) {
         }
 
         char[] separators = {'-', '_', ' ', ':', '(', ')'};
-        return camelize(replaceSpecialCharacters(WordUtils.capitalizeFully(StringUtils.lowerCase(name), separators)
-                .replaceAll("[-_ :\\(\\)]", "")));
+        return camelize(replaceSpecialCharacters(DASH_UNDERSCORE_SPACE_COLON_PARENTHESES.matcher(WordUtils.capitalizeFully(StringUtils.lowerCase(name), separators))
+                .replaceAll("")));
     }
 
     private String replaceSpecialCharacters(String name) {
@@ -510,7 +510,7 @@ private String replaceSpecialCharacters(String name) {
         }
 
         // Fallback, replace unknowns with underscore.
-        name = name.replaceAll("\\W+", "_");
+        name = NON_WORD_PLUS.matcher(name).replaceAll("_");
 
         return name;
     }
@@ -547,12 +547,12 @@ public String toVarName(String name) {
         name = sanitizeName(name);
 
         // if it's all upper case, do nothing
-        if (name.matches("^[A-Z_]*$")) {
+        if (ALL_UPPER_UNDERSCORE.matcher(name).matches()) {
             return name;
         }
 
         // for reserved word or word starting with number, append _
-        if (isReservedWord(name) || name.matches("^\\d.*")) {
+        if (isReservedWord(name) || STARTS_WITH_DIGIT.matcher(name).matches()) {
             name = escapeReservedWord(name);
         }
         return name;
@@ -564,10 +564,10 @@ public String toParamName(String name) {
         name = sanitizeName(name);
 
         // replace - with _ e.g. created-at => created_at
-        name = name.replaceAll("-", "_");
+        name = MINUS.matcher(name).replaceAll("_");
 
         // if it's all upper case, do nothing
-        if (name.matches("^[A-Z_]*$")) {
+        if (ALL_UPPER_UNDERSCORE.matcher(name).matches()) {
             return name;
         }
 
@@ -581,7 +581,7 @@ public String toParamName(String name) {
         }
 
         // for words starting with number, prepend _
-        if (name.matches("^\\d.*")) {
+        if (STARTS_WITH_DIGIT.matcher(name).matches()) {
             name = "_" + name;
         }
 
@@ -595,14 +595,14 @@ public String toModelFilename(String name) {
         name = sanitizeName(name);
 
         // replace - with _ e.g. created-at => created_at
-        name = name.replaceAll("-", "_");
+        name = MINUS.matcher(name).replaceAll("_");
 
         if (isReservedWord(name)) {
             name = escapeReservedWord(name);
         }
 
         // for words starting with number, prepend A
-        if (name.matches("^\\d.*")) {
+        if (STARTS_WITH_DIGIT.matcher(name).matches()) {
             name = "A" + name;
         }
 
@@ -637,7 +637,7 @@ public String toModelName(String name) {
         }
 
         // model name starts with number
-        if (name.matches("^\\d.*")) {
+        if (STARTS_WITH_DIGIT.matcher(name).matches()) {
             // e.g. 200Response => Model200Response (after camelize)
             String modelName = "Model" + name;
             LOGGER.warn("{} (model name starts with number) cannot be used as model name. Renamed to {}", name,
diff --git a/modules/openapi-generator/src/main/java/org/openapitools/codegen/templating/mustache/KebabCaseLambda.java b/modules/openapi-generator/src/main/java/org/openapitools/codegen/templating/mustache/KebabCaseLambda.java
index af384969debc..00bd67a95cd6 100644
--- a/modules/openapi-generator/src/main/java/org/openapitools/codegen/templating/mustache/KebabCaseLambda.java
+++ b/modules/openapi-generator/src/main/java/org/openapitools/codegen/templating/mustache/KebabCaseLambda.java
@@ -36,21 +36,25 @@
  * {{#kebabcase}}{{summary}}{{/kebabcase}}
  * </pre>
  */
+import java.util.regex.Pattern;
+
 public class KebabCaseLambda implements Mustache.Lambda {
+
+    private static final Pattern PACKAGE_SEPARATOR = Pattern.compile("\\.");
+    private static final Pattern SPECIAL           = Pattern.compile("[^A-Za-z0-9_]");
+    private static final Pattern FIRST_PATTERN     = Pattern.compile("([A-Z]+)([A-Z][a-z])");
+    private static final Pattern SECOND_PATTERN    = Pattern.compile("([a-z\\d])([A-Z])");
+
+    private static final String SPACE_REPLACEMENT  = "$1 $2";
+
     @Override
     public void execute(Template.Fragment fragment, Writer writer) throws IOException {
         String text = fragment.execute();
 
-        String SPECIAL = "[^A-Za-z0-9_]";
-        String firstPattern = "([A-Z]+)([A-Z][a-z])";
-        String secondPattern = "([a-z\\d])([A-Z])";
-        String replacementPattern = "$1 $2";
-        // Replace package separator with slash.
-        text = text.replaceAll("\\.", "/");
-        text = text.replaceAll(SPECIAL, "");
-        // Replace capital letter with _ plus lowercase letter.
-        text = text.replaceAll(firstPattern, replacementPattern);
-        text = text.replaceAll(secondPattern, replacementPattern);
+        text = PACKAGE_SEPARATOR.matcher(text).replaceAll("/");
+        text = SPECIAL.matcher(text).replaceAll("");
+        text = FIRST_PATTERN.matcher(text).replaceAll(SPACE_REPLACEMENT);
+        text = SECOND_PATTERN.matcher(text).replaceAll(SPACE_REPLACEMENT);
         text = text.replace('_', '-');
         text = text.replace(' ', '-');
         text = text.toLowerCase(Locale.ROOT);
diff --git a/modules/openapi-generator/src/main/java/org/openapitools/codegen/utils/ModelUtils.java b/modules/openapi-generator/src/main/java/org/openapitools/codegen/utils/ModelUtils.java
index 3e355713e7f9..95a88ee7566a 100644
--- a/modules/openapi-generator/src/main/java/org/openapitools/codegen/utils/ModelUtils.java
+++ b/modules/openapi-generator/src/main/java/org/openapitools/codegen/utils/ModelUtils.java
@@ -2017,7 +2017,7 @@ private static ObjectMapper getRightMapper(String data) {
      */
     public static JsonNode readWithInfo(String location, List<AuthorizationValue> auths) throws Exception {
         String data;
-        location = location.replaceAll("\\\\", "/");
+        location = location.replace("\\", "/");
         if (location.toLowerCase(Locale.ROOT).startsWith("http")) {
             data = RemoteUrl.urlToString(location, auths);
         } else {
diff --git a/modules/openapi-generator/src/main/java/org/openapitools/codegen/utils/PatternCache.java b/modules/openapi-generator/src/main/java/org/openapitools/codegen/utils/PatternCache.java
new file mode 100644
index 000000000000..fa68699129ae
--- /dev/null
+++ b/modules/openapi-generator/src/main/java/org/openapitools/codegen/utils/PatternCache.java
@@ -0,0 +1,92 @@
+/*
+ * Copyright 2018 OpenAPI-Generator Contributors (https://openapi-generator.tech)
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     https://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.openapitools.codegen.utils;
+
+import com.github.benmanes.caffeine.cache.Cache;
+import com.github.benmanes.caffeine.cache.Caffeine;
+
+import java.util.regex.Pattern;
+
+/**
+ * A shared, process-wide cache of compiled {@link Pattern} objects, keyed by regex string
+ * (and optional flags).
+ *
+ * <h3>Motivation</h3>
+ * {@link Pattern#compile(String)} is non-trivial: it parses and compiles the regex into an
+ * internal automaton. When the same literal regex is compiled inside a hot loop (e.g. once
+ * per property name, per operation, or per model), the overhead accumulates. This cache
+ * ensures each distinct {@code (regex, flags)} pair is compiled at most once.
+ *
+ * <h3>Thread safety</h3>
+ * Backed by a Caffeine cache; all operations are thread-safe. Caffeine's internal striped
+ * locking means concurrent requests for the same key result in only one compilation.
+ *
+ * <h3>Memory</h3>
+ * The cache is bounded at {@value #MAX_SIZE} entries via LRU eviction, which is effectively
+ * unlimited for any single codegen run (realistic specs have at most dozens of distinct
+ * patterns) while protecting long-lived server processes (e.g. openapi-generator-online)
+ * from unbounded growth caused by user-supplied {@code pattern:} values.
+ *
+ * <h3>What goes here vs. {@code static final Pattern}</h3>
+ * Use this cache only for <em>dynamic</em> pattern keys — i.e. patterns whose regex string
+ * is not known at compile time (user config, OpenAPI {@code pattern:} field values, etc.).
+ * Fixed literal patterns that appear in a single class should remain
+ * {@code private static final Pattern} constants; they are resolved at class-load time and
+ * accessed via a direct field read, which is faster than any map lookup.
+ */
+public final class PatternCache {
+
+    /** Maximum number of cached entries before LRU eviction kicks in. */
+    static final int MAX_SIZE = 10_000;
+
+    private static final Cache<String, Pattern> CACHE = Caffeine.newBuilder()
+            .maximumSize(MAX_SIZE)
+            .build();
+
+    private PatternCache() {
+        // utility class – no instances
+    }
+
+    /**
+     * Returns a compiled {@link Pattern} for {@code regex} with no flags, compiling it on the
+     * first call and returning the cached instance on subsequent calls.
+     *
+     * @param regex the regular-expression string (must not be {@code null})
+     * @return a compiled {@link Pattern}
+     */
+    public static Pattern get(String regex) {
+        return CACHE.get(regex, Pattern::compile);
+    }
+
+    /**
+     * Returns a compiled {@link Pattern} for {@code regex} with the given {@code flags},
+     * compiling it on the first call and returning the cached instance on subsequent calls.
+     *
+     * <p>The cache key encodes both the regex string and the flags value so that the same
+     * regex compiled with different flags (e.g. {@link Pattern#UNICODE_CHARACTER_CLASS})
+     * is stored as a separate entry.
+     *
+     * @param regex the regular-expression string (must not be {@code null})
+     * @param flags match flags, as accepted by {@link Pattern#compile(String, int)}
+     * @return a compiled {@link Pattern}
+     */
+    public static Pattern get(String regex, int flags) {
+        // NUL character as separator is safe because it cannot appear in a valid regex string.
+        return CACHE.get(regex + '\0' + flags, k -> Pattern.compile(regex, flags));
+    }
+}
+
diff --git a/modules/openapi-generator/src/main/java/org/openapitools/codegen/utils/SemVer.java b/modules/openapi-generator/src/main/java/org/openapitools/codegen/utils/SemVer.java
index 0dc350677794..0ecddd4b1fa9 100644
--- a/modules/openapi-generator/src/main/java/org/openapitools/codegen/utils/SemVer.java
+++ b/modules/openapi-generator/src/main/java/org/openapitools/codegen/utils/SemVer.java
@@ -17,14 +17,18 @@
 
 package org.openapitools.codegen.utils;
 
+import java.util.regex.Pattern;
+
 public class SemVer implements Comparable<SemVer> {
 
+    private static final Pattern DOT = Pattern.compile("\\.");
+
     public final int major;
     public final int minor;
     public final int revision;
 
     public SemVer(String versionString) {
-        String[] tokens = versionString.split("\\.");
+        String[] tokens = DOT.split(versionString);
         major = Integer.parseInt(tokens[0]);
         minor = tokens.length < 2 ? 0 : Integer.parseInt(tokens[1]);
         revision = tokens.length < 3 ? 0 : Integer.parseInt(tokens[2]);
diff --git a/modules/openapi-generator/src/main/java/org/openapitools/codegen/utils/StringUtils.java b/modules/openapi-generator/src/main/java/org/openapitools/codegen/utils/StringUtils.java
index 18517bed319e..b043a77fc3bb 100644
--- a/modules/openapi-generator/src/main/java/org/openapitools/codegen/utils/StringUtils.java
+++ b/modules/openapi-generator/src/main/java/org/openapitools/codegen/utils/StringUtils.java
@@ -56,10 +56,10 @@ public class StringUtils {
                 .build();
     }
 
-    private static Pattern capitalLetterPattern = Pattern.compile("([A-Z]+)([A-Z][a-z][a-z]+)");
-    private static Pattern lowercasePattern = Pattern.compile("([a-z\\d])([A-Z])");
-    private static Pattern pkgSeparatorPattern = Pattern.compile("\\.");
-    private static Pattern dollarPattern = Pattern.compile("\\$");
+    private static final Pattern CAPITAL_LETTER_PATTERN = Pattern.compile("([A-Z]+)([A-Z][a-z][a-z]+)");
+    private static final Pattern LOWERCASE_PATTERN = Pattern.compile("([a-z\\d])([A-Z])");
+    private static final Pattern PKG_SEPARATOR_PATTERN = Pattern.compile("\\.");
+    private static final Pattern DOLLAR_PATTERN = Pattern.compile("\\$");
 
     /**
      * Underscore the given word.
@@ -74,12 +74,12 @@ public static String underscore(final String word) {
             String result;
             String replacementPattern = "$1_$2";
             // Replace package separator with slash.
-            result = pkgSeparatorPattern.matcher(wordToUnderscore).replaceAll("/");
+            result = PKG_SEPARATOR_PATTERN.matcher(wordToUnderscore).replaceAll("/");
             // Replace $ with two underscores for inner classes.
-            result = dollarPattern.matcher(result).replaceAll("__");
+            result = DOLLAR_PATTERN.matcher(result).replaceAll("__");
             // Replace capital letter with _ plus lowercase letter.
-            result = capitalLetterPattern.matcher(result).replaceAll(replacementPattern);
-            result = lowercasePattern.matcher(result).replaceAll(replacementPattern);
+            result = CAPITAL_LETTER_PATTERN.matcher(result).replaceAll(replacementPattern);
+            result = LOWERCASE_PATTERN.matcher(result).replaceAll(replacementPattern);
             result = result.replace('-', '_');
             // replace space with underscore
             result = result.replace(' ', '_');
@@ -88,6 +88,7 @@ public static String underscore(final String word) {
         });
     }
 
+    private static final Pattern UNDERSCORE_OR_SPACE = Pattern.compile("[_ ]+");
     /**
      * Dashize the given word.
      *
@@ -95,7 +96,7 @@ public static String underscore(final String word) {
      * @return The dashized version of the word, e.g. "my-name"
      */
     public static String dashize(String word) {
-        return underscore(word).replaceAll("[_ ]+", "-");
+        return UNDERSCORE_OR_SPACE.matcher(underscore(word)).replaceAll("-");
     }
 
     /**
@@ -110,12 +111,13 @@ public static String camelize(String word) {
         return camelize(word, UPPERCASE_FIRST_CHAR);
     }
 
-    private static Pattern camelizeSlashPattern = Pattern.compile("\\/(.?)");
-    private static Pattern camelizeUppercasePattern = Pattern.compile("(\\.?)(\\w)([^\\.]*)$");
-    private static Pattern camelizeUnderscorePattern = Pattern.compile("(_)(.)");
-    private static Pattern camelizeHyphenPattern = Pattern.compile("(-)(.)");
-    private static Pattern camelizeDollarPattern = Pattern.compile("\\$");
-    private static Pattern camelizeSimpleUnderscorePattern = Pattern.compile("_");
+    private static final Pattern CAMELIZE_SLASH_PATTERN = Pattern.compile("/(.?)");
+    private static final Pattern CAMELIZE_UPPERCASE_PATTERN = Pattern.compile("(\\.?)(\\w)([^.]*)$");
+    private static final Pattern CAMELIZE_UNDERSCORE_PATTERN = Pattern.compile("(_)(.)");
+    private static final Pattern CAMELIZE_HYPHEN_PATTERN = Pattern.compile("(-)(.)");
+    private static final Pattern CAMELIZE_DOLLAR_PATTERN = Pattern.compile("\\$");
+    private static final Pattern CAMELIZE_SIMPLE_UNDERSCORE_PATTERN = Pattern.compile("_");
+    private static final Pattern DOT = Pattern.compile("\\.");
 
     /**
      * Camelize name (parameter, property, method, etc)
@@ -131,14 +133,14 @@ public static String camelize(final String inputWord, CamelizeOption camelizeOpt
             String word = pair.getKey();
             CamelizeOption option = pair.getValue();
             // Replace all slashes with dots (package separator)
-            Matcher m = camelizeSlashPattern.matcher(word);
+            Matcher m = CAMELIZE_SLASH_PATTERN.matcher(word);
             while (m.find()) {
                 word = m.replaceFirst("." + m.group(1).replace("\\", "\\\\")/*.toUpperCase()*/);
-                m = camelizeSlashPattern.matcher(word);
+                m = CAMELIZE_SLASH_PATTERN.matcher(word);
             }
 
             // case out dots
-            String[] parts = word.split("\\.");
+            String[] parts = DOT.split(word);
             StringBuilder f = new StringBuilder();
             for (String z : parts) {
                 if (z.length() > 0) {
@@ -147,38 +149,38 @@ public static String camelize(final String inputWord, CamelizeOption camelizeOpt
             }
             word = f.toString();
 
-            m = camelizeSlashPattern.matcher(word);
+            m = CAMELIZE_SLASH_PATTERN.matcher(word);
             while (m.find()) {
                 word = m.replaceFirst(Character.toUpperCase(m.group(1).charAt(0)) + m.group(1).substring(1)/*.toUpperCase()*/);
-                m = camelizeSlashPattern.matcher(word);
+                m = CAMELIZE_SLASH_PATTERN.matcher(word);
             }
 
             // Uppercase the class name.
-            m = camelizeUppercasePattern.matcher(word);
+            m = CAMELIZE_UPPERCASE_PATTERN.matcher(word);
             if (m.find()) {
                 String rep = m.group(1) + m.group(2).toUpperCase(Locale.ROOT) + m.group(3);
-                rep = camelizeDollarPattern.matcher(rep).replaceAll("\\\\\\$");
+                rep = CAMELIZE_DOLLAR_PATTERN.matcher(rep).replaceAll("\\\\\\$");
                 word = m.replaceAll(rep);
             }
 
             // Remove all underscores (underscore_case to camelCase)
-            m = camelizeUnderscorePattern.matcher(word);
+            m = CAMELIZE_UNDERSCORE_PATTERN.matcher(word);
             while (m.find()) {
                 String original = m.group(2);
                 String upperCase = original.toUpperCase(Locale.ROOT);
                 if (original.equals(upperCase)) {
-                    word = camelizeSimpleUnderscorePattern.matcher(word).replaceFirst("");
+                    word = CAMELIZE_SIMPLE_UNDERSCORE_PATTERN.matcher(word).replaceFirst("");
                 } else {
                     word = m.replaceFirst(upperCase);
                 }
-                m = camelizeUnderscorePattern.matcher(word);
+                m = CAMELIZE_UNDERSCORE_PATTERN.matcher(word);
             }
 
             // Remove all hyphens (hyphen-case to camelCase)
-            m = camelizeHyphenPattern.matcher(word);
+            m = CAMELIZE_HYPHEN_PATTERN.matcher(word);
             while (m.find()) {
                 word = m.replaceFirst(m.group(2).toUpperCase(Locale.ROOT));
-                m = camelizeHyphenPattern.matcher(word);
+                m = CAMELIZE_HYPHEN_PATTERN.matcher(word);
             }
 
             switch (option) {
@@ -191,7 +193,7 @@ public static String camelize(final String inputWord, CamelizeOption camelizeOpt
             }
 
             // remove all underscore
-            word = camelizeSimpleUnderscorePattern.matcher(word).replaceAll("");
+            word = CAMELIZE_SIMPLE_UNDERSCORE_PATTERN.matcher(word).replaceAll("");
             return word;
         });
     }
diff --git a/modules/openapi-generator/src/main/java/org/openapitools/codegen/utils/URLPathUtils.java b/modules/openapi-generator/src/main/java/org/openapitools/codegen/utils/URLPathUtils.java
index 47c98f557411..a7bb6460eba7 100644
--- a/modules/openapi-generator/src/main/java/org/openapitools/codegen/utils/URLPathUtils.java
+++ b/modules/openapi-generator/src/main/java/org/openapitools/codegen/utils/URLPathUtils.java
@@ -38,7 +38,12 @@ public class URLPathUtils {
 
     private static final Logger LOGGER = LoggerFactory.getLogger(URLPathUtils.class);
     public static final String LOCAL_HOST = "http://localhost";
-    public static final Pattern VARIABLE_PATTERN = Pattern.compile("(?<!\\$)\\{([^\\}]+)\\}");
+    public static final Pattern VARIABLE_PATTERN = Pattern.compile("(?<!\\$)\\{([^}]+)}");
+
+    /** Matches a URL that already has a valid scheme (e.g. {@code http://}, {@code https://}). */
+    private static final Pattern URL_WITH_SCHEME = Pattern.compile("[a-zA-Z][0-9a-zA-Z.+\\-]+://.+");
+    /** Matches a relative server URL whose path consists entirely of valid path segments. */
+    private static final Pattern RELATIVE_PATH_URL = Pattern.compile("^(/[\\w.~@-]+)+");
 
     // TODO: This should probably be moved into generator/workflow type rather than a static like this.
     public static URL getServerURL(OpenAPI openAPI, Map<String, String> userDefinedVariables) {
@@ -210,7 +215,7 @@ private static String sanitizeUrl(String url) {
             } else if (url.startsWith("/")) {
                 url = LOCAL_HOST + url;
                 once(LOGGER).info("'host' (OAS 2.0) or 'servers' (OAS 3.0) not defined in the spec. Default to [{}] for server URL [{}]", LOCAL_HOST, url);
-            } else if (!url.matches("[a-zA-Z][0-9a-zA-Z.+\\-]+://.+")) {
+            } else if (!URL_WITH_SCHEME.matcher(url).matches()) {
                 // Add http scheme for urls without a scheme.
                 // 2.0 spec is restricted to the following schemes: "http", "https", "ws", "wss"
                 // 3.0 spec does not have an enumerated list of schemes
@@ -235,7 +240,7 @@ private static URL getDefaultUrl() {
     public static boolean isRelativeUrl(List<Server> servers) {
         if (servers != null && servers.size() > 0) {
             final Server firstServer = servers.get(0);
-            return Pattern.matches("^(\\/[\\w\\d.~@-]+)+", firstServer.getUrl());
+            return RELATIVE_PATH_URL.matcher(firstServer.getUrl()).matches();
         }
         return false;
     }
diff --git a/modules/openapi-generator/src/test/java/org/openapitools/codegen/utils/PatternCacheTest.java b/modules/openapi-generator/src/test/java/org/openapitools/codegen/utils/PatternCacheTest.java
new file mode 100644
index 000000000000..b46b82732b57
--- /dev/null
+++ b/modules/openapi-generator/src/test/java/org/openapitools/codegen/utils/PatternCacheTest.java
@@ -0,0 +1,104 @@
+/*
+ * Copyright 2018 OpenAPI-Generator Contributors (https://openapi-generator.tech)
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     https://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.openapitools.codegen.utils;
+
+import org.testng.Assert;
+import org.testng.annotations.Test;
+
+import java.util.ArrayList;
+import java.util.List;
+import java.util.concurrent.Callable;
+import java.util.concurrent.ExecutorService;
+import java.util.concurrent.Executors;
+import java.util.concurrent.Future;
+import java.util.regex.Pattern;
+
+public class PatternCacheTest {
+
+    @Test
+    public void testSameInstanceReturnedForSameRegex() {
+        Pattern first  = PatternCache.get("\\W+");
+        Pattern second = PatternCache.get("\\W+");
+        Assert.assertSame(first, second,
+                "PatternCache must return the same Pattern instance for the same regex string");
+    }
+
+    @Test
+    public void testSameInstanceReturnedForSameRegexAndFlags() {
+        Pattern first  = PatternCache.get("\\W+", Pattern.UNICODE_CHARACTER_CLASS);
+        Pattern second = PatternCache.get("\\W+", Pattern.UNICODE_CHARACTER_CLASS);
+        Assert.assertSame(first, second,
+                "PatternCache must return the same Pattern instance for identical (regex, flags) pairs");
+    }
+
+    @Test
+    public void testDifferentInstanceForDifferentFlags() {
+        Pattern noFlags   = PatternCache.get("\\W+");
+        Pattern withFlags = PatternCache.get("\\W+", Pattern.UNICODE_CHARACTER_CLASS);
+        Assert.assertNotSame(noFlags, withFlags,
+                "PatternCache must store separate entries for the same regex compiled with different flags");
+        Assert.assertEquals(noFlags.flags() & Pattern.UNICODE_CHARACTER_CLASS, 0,
+                "Pattern compiled without flags must not have UNICODE_CHARACTER_CLASS set");
+        Assert.assertEquals(withFlags.flags() & Pattern.UNICODE_CHARACTER_CLASS, Pattern.UNICODE_CHARACTER_CLASS,
+                "Pattern compiled with UNICODE_CHARACTER_CLASS must have that flag set " +
+                "(note: the JVM may also implicitly set UNICODE_CASE=64, so exact equality is not checked)");
+    }
+
+    @Test
+    public void testDifferentInstanceForDifferentRegex() {
+        Pattern a = PatternCache.get("\\d+");
+        Pattern b = PatternCache.get("\\W+");
+        Assert.assertNotSame(a, b,
+                "PatternCache must store separate entries for different regex strings");
+    }
+
+    @Test
+    public void testPatternFunctionallyCorrect() {
+        Pattern pattern = PatternCache.get("\\d+");
+        Assert.assertTrue(pattern.matcher("123").matches());
+        Assert.assertFalse(pattern.matcher("abc").matches());
+    }
+
+    @Test
+    public void testConcurrentAccessReturnsSameInstance() throws Exception {
+        final String regex = "concurrent-test-[a-z]+";
+        final int threads = 20;
+
+        ExecutorService executor = Executors.newFixedThreadPool(threads);
+        List<Callable<Pattern>> tasks = new ArrayList<>(threads);
+        for (int i = 0; i < threads; i++) {
+            tasks.add(() -> PatternCache.get(regex));
+        }
+
+        List<Future<Pattern>> futures = executor.invokeAll(tasks);
+        executor.shutdown();
+
+        Pattern expected = futures.get(0).get();
+        for (Future<Pattern> future : futures) {
+            Assert.assertSame(future.get(), expected,
+                    "All concurrent callers must receive the same cached Pattern instance");
+        }
+    }
+
+    @Test
+    public void testMaxSizeIsReasonable() {
+        Assert.assertTrue(PatternCache.MAX_SIZE >= 1_000,
+                "PatternCache.MAX_SIZE should be at least 1000 to cover realistic workloads");
+    }
+}
+
+