feat: optimize SortUtils.swap by skipping operations for equal indices (#5266)

* Refactor: adding check to swap method in SortUtils

* Checkstyle: fix formatting

* Checkstyle: fix formatting, and redundant braces

* fix: adding flipped tests, removed messages from tests

* checkstyle: fix indent

* style: mark `temp` as `final`

* tests: remove test case with empty array

Such calls should be excluded.

---------

Co-authored-by: Piotr Idzik <[email protected]>

Author: alxkm

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

@@ -17,9 +17,11 @@ private SortUtils() {
      * @param <T>   the type of elements in the array
      */
     public static <T> void swap(T[] array, int i, int j) {
-        T temp = array[i];
-        array[i] = array[j];
-        array[j] = temp;
+        if (i != j) {
+            final T temp = array[i];
+            array[i] = array[j];
+            array[j] = temp;
+        }
     }
 
     /**

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

@@ -1,10 +1,15 @@
 package com.thealgorithms.sorts;
 
+import static org.junit.jupiter.api.Assertions.assertArrayEquals;
 import static org.junit.jupiter.api.Assertions.assertFalse;
 import static org.junit.jupiter.api.Assertions.assertTrue;
 
 import java.util.List;
+import java.util.stream.Stream;
 import org.junit.jupiter.api.Test;
+import org.junit.jupiter.params.ParameterizedTest;
+import org.junit.jupiter.params.provider.Arguments;
+import org.junit.jupiter.params.provider.MethodSource;
 
 class SortUtilsTest {
 
@@ -67,4 +72,23 @@ void isSortedListFalse() {
         List<Integer> array3 = List.of(5, 4, 3, 2, 1);
         assertFalse(SortUtils.isSorted(array3));
     }
+
+    @ParameterizedTest
+    @MethodSource("provideArraysForSwap")
+    public <T> void testSwap(T[] array, int i, int j, T[] expected) {
+        SortUtils.swap(array, i, j);
+        assertArrayEquals(expected, array);
+    }
+
+    @ParameterizedTest
+    @MethodSource("provideArraysForSwap")
+    public <T> void testSwapFlippedIndices(T[] array, int i, int j, T[] expected) {
+        SortUtils.swap(array, j, i);
+        assertArrayEquals(expected, array);
+    }
+
+    private static Stream<Arguments> provideArraysForSwap() {
+        return Stream.of(Arguments.of(new Integer[] {1, 2, 3, 4}, 1, 2, new Integer[] {1, 3, 2, 4}), Arguments.of(new Integer[] {1, 2, 3, 4}, 0, 3, new Integer[] {4, 2, 3, 1}), Arguments.of(new Integer[] {1, 2, 3, 4}, 2, 2, new Integer[] {1, 2, 3, 4}),
+            Arguments.of(new String[] {"a", "b", "c", "d"}, 0, 3, new String[] {"d", "b", "c", "a"}), Arguments.of(new String[] {null, "b", "c", null}, 0, 3, new String[] {null, "b", "c", null}));
+    }
 }