Added PriorityQueueSort algorithm and Tests

src/main/java/com/thealgorithms/sorts/PriorityQueueSort.java

@@ -0,0 +1,49 @@
+package com.thealgorithms.sorts;
+
+import java.util.PriorityQueue;
+
+/**
+ * Sorts an array using Java's PriorityQueue (Min-Heap).
+ *
+ * <p>Example: Input: [7, 2, 9, 4, 1] Output: [1, 2, 4, 7, 9]
+ *
+ * <p>Time Complexity:
+ * - Inserting n elements into the PriorityQueue → O(n log n)
+ * - Polling n elements → O(n log n)
+ * - Total: O(n log n)
+ *
+ * <p>Space Complexity: O(n) for the PriorityQueue
+ *
+ * @see <a href="https://en.wikipedia.org/wiki/Heap_(data_structure)">
+ *     Heap / PriorityQueue</a>
+ */
+public final class PriorityQueueSort {
+
+    // Private constructor to prevent instantiation (utility class)
+    private PriorityQueueSort() {
+    }
+
+    /**
+     * Sorts the given array in ascending order using a PriorityQueue.
+     *
+     * @param arr the array to be sorted
+     * @return the sorted array (in-place)
+     */
+    public static int[] sort(int[] arr) {
+        if (arr == null || arr.length == 0) {
+            return arr;
+        }
+
+        PriorityQueue<Integer> pq = new PriorityQueue<>();
+        for (int num : arr) {
+            pq.offer(num);
+        }
+
+        int i = 0;
+        while (!pq.isEmpty()) {
+            arr[i++] = pq.poll();
+        }
+
+        return arr;
+    }
+}

src/test/java/com/thealgorithms/sorts/PriorityQueueSortTest.java

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+package com.thealgorithms.sorts;
+
+import static org.junit.jupiter.api.Assertions.assertArrayEquals;
+
+import org.junit.jupiter.api.Test;
+
+class PriorityQueueSortTest {
+
+    @Test
+    void testNullArray() {
+        int[] input = null;
+        assertArrayEquals(null, PriorityQueueSort.sort(input));
+    }
+
+    @Test
+    void testSingleElementArray() {
+        int[] input = {5};
+        int[] expected = {5};
+        assertArrayEquals(expected, PriorityQueueSort.sort(input));
+    }
+
+    @Test
+    void testSortNormalArray() {
+        int[] input = {7, 2, 9, 4, 1};
+        int[] expected = {1, 2, 4, 7, 9};
+        assertArrayEquals(expected, PriorityQueueSort.sort(input));
+    }
+
+    @Test
+    void testEmptyArray() {
+        int[] input = {};
+        int[] expected = {};
+        assertArrayEquals(expected, PriorityQueueSort.sort(input));
+    }
+
+    @Test
+    void testNegativeNumbers() {
+        int[] input = {3, -1, 2, -5, 0};
+        int[] expected = {-5, -1, 0, 2, 3};
+        assertArrayEquals(expected, PriorityQueueSort.sort(input));
+    }
+
+    @Test
+    void testAlreadySortedArray() {
+        int[] input = {1, 2, 3, 4, 5};
+        int[] expected = {1, 2, 3, 4, 5};
+        assertArrayEquals(expected, PriorityQueueSort.sort(input));
+    }
+
+    @Test
+    void testArrayWithDuplicates() {
+        int[] input = {5, 1, 3, 3, 2, 5};
+        int[] expected = {1, 2, 3, 3, 5, 5};
+        assertArrayEquals(expected, PriorityQueueSort.sort(input));
+    }
+}