BAEL-6225 Refactor code and move package. (#14132)

* BAEL-6225 Refactor code and move package.

* BAEL-6225 Move code to core-java-lang-oop-patterns.

* BAEL-6225 Refactor test name.

* BAEL-6225 Refactor test name.

* BAEL-6225 Update with singleton instances.

core-java-modules/core-java-lang-oop-patterns/src/main/java/com/baeldung/stateless/BubbleSort.java

@@ -0,0 +1,20 @@
+package com.baeldung.stateless;
+
+public enum BubbleSort implements SortingStrategy {
+    
+    INSTANCE;
+
+    @Override
+    public void sort(int[] array) {
+        int n = array.length;
+        for (int i = 0; i < n - 1; i++) {
+            for (int j = 0; j < n - i - 1; j++) {
+                if (array[j] > array[j + 1]) {
+                    int swap = array[j];
+                    array[j] = array[j + 1];
+                    array[j + 1] = swap;
+                }
+            }
+        }
+    }
+}

core-java-modules/core-java-lang-oop-patterns/src/main/java/com/baeldung/stateless/QuickSort.java

@@ -0,0 +1,36 @@
+package com.baeldung.stateless;
+
+public enum QuickSort implements SortingStrategy {
+    
+    INSTANCE;
+
+    @Override
+    public void sort(int[] array) {
+        quickSort(array, 0, array.length - 1);
+    }
+    
+    private void quickSort(int[] array, int begin, int end) {
+        if (begin < end) {
+            int pi = partition(array, begin, end);
+            quickSort(array, begin, pi - 1);
+            quickSort(array, pi + 1, end);
+        }
+    }    
+
+    private int partition(int[] array, int low, int high) {
+        int pivot = array[high];
+        int i = low - 1;
+        for (int j = low; j < high; j++) {
+            if (array[j] < pivot) {
+                i++;
+                int swap = array[i];
+                array[i] = array[j];
+                array[j] = swap;
+            }
+        }
+        int swap = array[i + 1];
+        array[i + 1] = array[high];
+        array[high] = swap;
+        return i + 1;
+    }
+}

core-java-modules/core-java-lang-oop-patterns/src/main/java/com/baeldung/stateless/SortingStrategy.java

@@ -0,0 +1,7 @@
+package com.baeldung.stateless;
+
+public interface SortingStrategy {
+    
+    public void sort(int[] array);
+
+}

core-java-modules/core-java-lang-oop-patterns/src/test/java/com/baeldung/stateless/ArraySortingUnitTest.java

@@ -0,0 +1,28 @@
+package com.baeldung.stateless;
+
+import static org.junit.Assert.assertArrayEquals;
+
+import org.junit.jupiter.api.Test;
+
+public class ArraySortingUnitTest {
+    
+    @Test
+    void givenArray_whenBubbleSorting_thenSorted() {
+        int[] arrayToSort = {17, 6, 11, 41, 5, 3, 4, -9};
+        int[] sortedArray = {-9, 3, 4, 5, 6, 11, 17, 41};
+        
+        SortingStrategy sortingStrategy = BubbleSort.INSTANCE;
+        sortingStrategy.sort(arrayToSort);
+        assertArrayEquals(sortedArray, arrayToSort);
+    }
+    
+    @Test
+    void givenArray_whenQuickSortSorting_thenSorted() {
+        int[] arrayToSort = {17, 6, 11, 41, 5, 3, 4, -9};
+        int[] sortedArray = {-9, 3, 4, 5, 6, 11, 17, 41};
+        
+        SortingStrategy sortingStrategy = QuickSort.INSTANCE;
+        sortingStrategy.sort(arrayToSort);
+        assertArrayEquals(sortedArray, arrayToSort);
+    }
+}