Add ReverseQueueRecursion.java: Reverse a Queue using recursion (#7281)

* Create ReverseQueueRecursion

Add ReverseQueueRecursion.java:
- Reverses a Queue using recursion (generic <T>)
- Includes unit tests in ReverseQueueRecursionTest.java
- Follows repo style (final class, private constructor, Javadoc)

* Create ReverseQueueRecursionTest.java

Add ReverseQueueRecursionTest as required by CONTRIBUTING.md

* Rename ReverseQueueRecursion to ReverseQueueRecursion.java

* Update ReverseQueueRecursion.java

* Update ReverseQueueRecursion.java

* Update ReverseQueueRecursion.java

* Update ReverseQueueRecursion.java

* Update ReverseQueueRecursionTest.java

* Update ReverseQueueRecursion.java

* Update ReverseQueueRecursionTest.java

* Update ReverseQueueRecursionTest.java

* Update ReverseQueueRecursion.java

* Update ReverseQueueRecursionTest.java

* Update ReverseQueueRecursionTest.java

* Update ReverseQueueRecursionTest.java

* Update ReverseQueueRecursionTest.java

* Update ReverseQueueRecursion.java

Author: Vasundhara117

src/main/java/com/thealgorithms/datastructures/queues/ReverseQueueRecursion.java

@@ -0,0 +1,28 @@
+package com.thealgorithms.datastructures.queues;
+
+import java.util.Queue;
+
+/**
+ * Reverse a queue using recursion.
+ */
+public final class ReverseQueueRecursion {
+    private ReverseQueueRecursion() {
+        // private constructor to prevent instantiation
+    }
+
+    /**
+     * Reverses the given queue recursively.
+     *
+     * @param queue the queue to reverse
+     * @param <T> the type of elements in the queue
+     */
+    public static <T> void reverseQueue(final Queue<T> queue) {
+        if (queue == null || queue.isEmpty()) {
+            return;
+        }
+
+        final T front = queue.poll();
+        reverseQueue(queue);
+        queue.add(front);
+    }
+}

src/test/java/com/thealgorithms/datastructures/queues/ReverseQueueRecursionTest.java

@@ -0,0 +1,54 @@
+package com.thealgorithms.datastructures.queues;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.junit.jupiter.api.Assertions.assertTrue;
+
+import java.util.LinkedList;
+import java.util.Queue;
+import org.junit.jupiter.api.Test;
+
+class ReverseQueueRecursionTest {
+    @Test
+    void testReverseMultipleElements() {
+        Queue<Integer> queue = new LinkedList<>();
+        queue.add(1);
+        queue.add(2);
+        queue.add(3);
+        queue.add(4);
+        ReverseQueueRecursion.reverseQueue(queue);
+        assertEquals(4, queue.poll());
+        assertEquals(3, queue.poll());
+        assertEquals(2, queue.poll());
+        assertEquals(1, queue.poll());
+        assertTrue(queue.isEmpty());
+    }
+
+    @Test
+    void testReverseSingleElement() {
+        Queue<Integer> queue = new LinkedList<>();
+        queue.add(42);
+        ReverseQueueRecursion.reverseQueue(queue);
+        assertEquals(42, queue.poll());
+        assertTrue(queue.isEmpty());
+    }
+
+    @Test
+    void testReverseEmptyQueue() {
+        Queue<Integer> queue = new LinkedList<>();
+        ReverseQueueRecursion.reverseQueue(queue);
+        assertTrue(queue.isEmpty());
+    }
+
+    @Test
+    void testReverseStringQueue() {
+        Queue<String> queue = new LinkedList<>();
+        queue.add("A");
+        queue.add("B");
+        queue.add("C");
+        ReverseQueueRecursion.reverseQueue(queue);
+        assertEquals("C", queue.poll());
+        assertEquals("B", queue.poll());
+        assertEquals("A", queue.poll());
+        assertTrue(queue.isEmpty());
+    }
+}