add null checker in test and more distinct in rabin function

Author: bri-harris

src/main/java/com/thealgorithms/randomized/ClosestPair.java

@@ -78,9 +78,7 @@ public static Object[] rabinRandomizedClosestPair(List<Point> points) {
 
         // Confirm neither closestA nor closestB are null
         if (closestA == null || closestB == null) {
-            closestA = points.get(0);
-            closestB = points.get(1);
-            delta = euclideanDistance(closestA, closestB);
+            return new Object[] {points.get(0), points.get(1), euclideanDistance(points.get(0), points.get(1))};
         }
 
         // Create a grid, We will use "Probabilistic Filtering" by only checking

src/test/java/com/thealgorithms/randomized/ClosestPairTest.java

@@ -23,6 +23,10 @@ void testStandardCaseClosestPair() {
     void testTwoDistinctPoints() {
         List<Point> points = Arrays.asList(new Point(1, 2), new Point(2, 3));
         Object[] closestPair = ClosestPair.rabinRandomizedClosestPair(points);
+
+        assertNotNull(closestPair[0]);
+        assertNotNull(closestPair[1]);
+
         assertTrue((closestPair[0].equals(points.get(0)) && closestPair[1].equals(points.get(1))) || (closestPair[1].equals(points.get(0)) && closestPair[0].equals(points.get(1))));
         assertEquals(closestPair[2], ClosestPair.euclideanDistance(points.get(0), points.get(1)));
     }