BAEL-9113 Synchronize Virtual Threads without Pinning in Java 24

core-java-modules/core-java-concurrency-advanced-7/pom.xml

@@ -20,10 +20,72 @@
             <version>${awaitility.version}</version>
             <scope>test</scope>
         </dependency>
+        <dependency>
+            <groupId>org.openjdk.jmh</groupId>
+            <artifactId>jmh-core</artifactId>
+            <version>${jmh.core.version}</version>
+        </dependency>
+        <dependency>
+            <groupId>org.openjdk.jmh</groupId>
+            <artifactId>jmh-generator-annprocess</artifactId>
+            <version>${jmh.core.version}</version>
+        </dependency>
     </dependencies>
 
+    <build>
+        <plugins>
+            <plugin>
+                <groupId>org.apache.maven.plugins</groupId>
+                <artifactId>maven-compiler-plugin</artifactId>
+                <configuration>
+                    <source>${maven.compiler.source.version}</source>
+                    <target>${maven.compiler.target.version}</target>
+                    <debug>false</debug>
+                    <compilerArgs>
+                        <arg>--enable-preview</arg>
+                    </compilerArgs>
+                    <annotationProcessorPaths>
+                        <path>
+                            <groupId>org.openjdk.jmh</groupId>
+                            <artifactId>jmh-generator-annprocess</artifactId>
+                            <version>${jmh.core.version}</version>
+                        </path>
+                    </annotationProcessorPaths>
+                </configuration>
+            </plugin>
+            <plugin>
+                <groupId>org.apache.maven.plugins</groupId>
+                <artifactId>maven-surefire-plugin</artifactId>
+                <configuration>
+                    <argLine>--enable-preview</argLine>
+                </configuration>
+            </plugin>
+            <plugin>
+                <groupId>org.apache.maven.plugins</groupId>
+                <artifactId>maven-shade-plugin</artifactId>
+                <executions>
+                    <execution>
+                        <phase>package</phase>
+                        <goals><goal>shade</goal></goals>
+                        <configuration>
+                            <finalName>benchmarks</finalName>
+                            <transformers>
+                                <transformer implementation="org.apache.maven.plugins.shade.resource.ManifestResourceTransformer">
+                                    <mainClass>org.openjdk.jmh.Main</mainClass>
+                                </transformer>
+                            </transformers>
+                        </configuration>
+                    </execution>
+                </executions>
+            </plugin>
+        </plugins>
+    </build>
+
     <properties>
         <awaitility.version>1.7.0</awaitility.version>
+        <maven.compiler.source.version>21</maven.compiler.source.version>
+        <maven.compiler.target.version>21</maven.compiler.target.version>
+        <jmh.core.version>1.37</jmh.core.version>
     </properties>
 
 </project>

core-java-modules/core-java-concurrency-advanced-7/src/main/java/com/baeldung/virtualthread/classinit/HeavyClass.java

@@ -0,0 +1,29 @@
+package com.baeldung.virtualthread.classinit;
+
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+public class HeavyClass {
+
+    private static final Logger LOGGER = LoggerFactory.getLogger(HeavyClass.class);
+
+    static {
+        try {
+            Thread.sleep(100);
+        } catch (InterruptedException ex) {
+            throw new RuntimeException(ex);
+        }
+
+        LOGGER.info("static initialization done");
+    }
+
+    {
+        try {
+            Thread.sleep(100);
+        } catch (InterruptedException ex) {
+            throw new RuntimeException(ex);
+        }
+
+        LOGGER.info("initialization done");
+    }
+}

core-java-modules/core-java-concurrency-advanced-7/src/main/java/com/baeldung/virtualthread/classloader/CustomClassLoader.java

@@ -0,0 +1,55 @@
+package com.baeldung.virtualthread.classloader;
+
+import java.io.IOException;
+import java.nio.file.Path;
+
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+class CustomClassLoader extends ClassLoader {
+
+    private static final Logger LOGGER = LoggerFactory.getLogger(CustomClassLoader.class);
+    private final Path classDir;
+
+    public CustomClassLoader(Path classDir) {
+        super(ClassLoader.getSystemClassLoader());
+        this.classDir = classDir;
+    }
+
+    @Override
+    protected Class<?> loadClass(String name, boolean resolve) throws ClassNotFoundException {
+        LOGGER.info("Load class for {}", name);
+
+        Class<?> clazz = findLoadedClass(name);
+
+        if (clazz == null) {
+            try {
+                clazz = findClass(name);
+            } catch (ClassNotFoundException ex) {
+                clazz = super.loadClass(name, resolve);
+            }
+        }
+
+        if (resolve) {
+            resolveClass(clazz);
+        }
+
+        return clazz;
+    }
+
+    @Override
+    protected Class<?> findClass(String name) throws ClassNotFoundException {
+        LOGGER.info("Finding class for {}", name);
+
+        try {
+            Path file = classDir.resolve(name.replace('.', '/') + ".class");
+            byte[] bytes = java.nio.file.Files.readAllBytes(file);
+            Thread.sleep(100);
+
+            return defineClass(name, bytes, 0, bytes.length);
+        } catch (InterruptedException | IOException ex) {
+            LOGGER.error("Error while finding class file {}", ex.getMessage());
+            throw new ClassNotFoundException(ex.getMessage(), ex);
+        }
+    }
+}

core-java-modules/core-java-concurrency-advanced-7/src/main/java/com/baeldung/virtualthread/classloader/MyClass.java

@@ -0,0 +1,6 @@
+package com.baeldung.virtualthread.classloader;
+
+public class MyClass {
+    public MyClass() {
+    }
+}

core-java-modules/core-java-concurrency-advanced-7/src/main/java/com/baeldung/virtualthread/foreignfunction/ForeignFunctionClass.java

@@ -0,0 +1,33 @@
+package com.baeldung.virtualthread.foreignfunction;
+
+import static java.lang.foreign.ValueLayout.JAVA_INT;
+import static java.lang.foreign.ValueLayout.JAVA_LONG;
+
+import java.lang.foreign.FunctionDescriptor;
+import java.lang.foreign.Linker;
+import java.lang.foreign.SymbolLookup;
+import java.lang.invoke.MethodHandle;
+
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+public class ForeignFunctionClass {
+
+    private static final Logger LOGGER = LoggerFactory.getLogger(ForeignFunctionClass.class);
+
+    public void execute() {
+        LOGGER.info("Running foreign function sleep...");
+
+        Linker linker = Linker.nativeLinker();
+        SymbolLookup stdlib = linker.defaultLookup();
+        MethodHandle sleep = linker.downcallHandle(stdlib.find("sleep")
+            .orElseThrow(), FunctionDescriptor.of(JAVA_INT, JAVA_LONG));
+
+        try {
+            sleep.invoke(100);
+        } catch (Throwable ex) {
+            System.out.println("Error in native sleep...");
+            throw new RuntimeException(ex);
+        }
+    }
+}

core-java-modules/core-java-concurrency-advanced-7/src/main/java/com/baeldung/virtualthread/nativemethod/NativeDemo.java

@@ -0,0 +1,10 @@
+package com.baeldung.virtualthread.nativemethod;
+
+public class NativeDemo {
+
+    static {
+        System.loadLibrary("native-lib");
+    }
+
+    public native String nativeCall();
+}

core-java-modules/core-java-concurrency-advanced-7/src/main/java/com/baeldung/virtualthread/synchronize/BenchmarkVirtualThread.java

@@ -0,0 +1,48 @@
+package com.baeldung.virtualthread.synchronize;
+
+import java.io.IOException;
+import java.util.ArrayList;
+import java.util.List;
+import java.util.UUID;
+import java.util.concurrent.TimeUnit;
+import java.util.stream.IntStream;
+
+import org.openjdk.jmh.annotations.Benchmark;
+import org.openjdk.jmh.annotations.BenchmarkMode;
+import org.openjdk.jmh.annotations.Fork;
+import org.openjdk.jmh.annotations.Measurement;
+import org.openjdk.jmh.annotations.Mode;
+import org.openjdk.jmh.annotations.OutputTimeUnit;
+import org.openjdk.jmh.annotations.Param;
+import org.openjdk.jmh.annotations.Scope;
+import org.openjdk.jmh.annotations.State;
+import org.openjdk.jmh.annotations.Warmup;
+
+@BenchmarkMode({ Mode.AverageTime, Mode.Throughput })
+@OutputTimeUnit(TimeUnit.SECONDS)
+@Warmup(iterations = 1, time = 5, timeUnit = TimeUnit.SECONDS)
+@Measurement(iterations = 3, time = 5, timeUnit = TimeUnit.SECONDS)
+@Fork(value = 2)
+@State(Scope.Benchmark)
+public class BenchmarkVirtualThread {
+
+    private final CartService cartService = new CartService();
+
+    @Param({ "100", "1000", "10000" })
+    private int CONCURRENCY;
+
+    @Benchmark
+    public void benchmark() throws InterruptedException, IOException {
+        List<Thread> threads = new ArrayList<>();
+        IntStream.range(0, CONCURRENCY).forEach(i -> threads.add(Thread.startVirtualThread(() -> cartService.update(UUID.randomUUID()
+                .toString(), 2))));
+
+        threads.forEach(th -> {
+            try {
+                th.join();
+            } catch (InterruptedException ex) {
+                throw new RuntimeException(ex);
+            }
+        });
+    }
+}

core-java-modules/core-java-concurrency-advanced-7/src/main/java/com/baeldung/virtualthread/synchronize/CartService.java

@@ -0,0 +1,43 @@
+package com.baeldung.virtualthread.synchronize;
+
+import java.util.HashMap;
+import java.util.Map;
+import java.util.concurrent.ConcurrentHashMap;
+
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+public class CartService {
+
+    private static final Logger LOGGER = LoggerFactory.getLogger(CartService.class);
+
+    private final Map<String, Integer> products;
+    private final Map<String, Object> locks = new ConcurrentHashMap<>();
+
+    public CartService() {
+        this.products = new HashMap<>();
+    }
+
+    public void update(String productId, int quantity) {
+        Object lock = locks.computeIfAbsent(productId, k -> new Object());
+
+        synchronized (lock) {
+            simulateAPI();
+            products.merge(productId, quantity, Integer::sum);
+        }
+
+        LOGGER.info("Updated Cart for {} {}", productId, quantity);
+    }
+
+    public Map<String, Integer> getProducts() {
+        return Map.copyOf(products);
+    }
+
+    private void simulateAPI() {
+        try {
+            Thread.sleep(50);
+        } catch (InterruptedException ex) {
+            throw new RuntimeException(ex);
+        }
+    }
+}

core-java-modules/core-java-concurrency-advanced-7/src/main/java/com/baeldung/virtualthread/synchronize/fixed/CartService.java

@@ -0,0 +1,53 @@
+package com.baeldung.virtualthread.synchronize.fixed;
+
+import java.util.HashMap;
+import java.util.Map;
+import java.util.concurrent.ConcurrentHashMap;
+import java.util.concurrent.TimeUnit;
+import java.util.concurrent.locks.Lock;
+import java.util.concurrent.locks.ReentrantLock;
+
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+public class CartService {
+
+    private static final Logger LOGGER = LoggerFactory.getLogger(CartService.class);
+
+    private final Map<String, Integer> products;
+    private final Map<String, ReentrantLock> locks = new ConcurrentHashMap<>();
+
+    public CartService() {
+        this.products = new HashMap<>();
+    }
+
+    public void update(String productId, int quantity) {
+        Lock lock = locks.computeIfAbsent(productId, k -> new ReentrantLock());
+
+        try {
+            if (lock.tryLock(500, TimeUnit.MILLISECONDS)) {
+                try {
+                    simulateAPI();
+                    products.merge(productId, quantity, Integer::sum);
+                } finally {
+                    lock.unlock();
+                }
+                LOGGER.info("Updated Cart for {} {}", productId, quantity);
+            }
+        } catch (InterruptedException ex) {
+            throw new RuntimeException(ex);
+        }
+    }
+
+    private void simulateAPI() {
+        try {
+            Thread.sleep(50);
+        } catch (InterruptedException ex) {
+            throw new RuntimeException(ex);
+        }
+    }
+
+    public Map<String, Integer> getProducts() {
+        return Map.copyOf(products);
+    }
+}