feature: Add ReverseArraySnippet class (iluwatar#181)

README.md

@@ -319,6 +319,29 @@ Inspired by [30 seconds of code](https://github.com/Chalarangelo/30-seconds-of-c
   }
 ```
 
+### Reverse array
+
+```java
+  public static <T> T[] reverseArray(T[] array, int start, int end) {
+    if (start > end || array == null) {
+     throw new
+        IllegalArgumentException("Invalid argument!");
+    }
+    int minimumSizeArrayForReversal = 2;
+    if (start == end || array.length < minimumSizeArrayForReversal) {
+      return array;
+    }
+    while (start < end) {
+      T temp = array[start];
+      array[start] = array[end];
+      array[end] = temp;
+      start++;
+      end--;
+    }
+    return array;
+  }
+```
+
 ## Encoding
 
 ### Base64 encode string

src/main/java/array/ReverseArraySnippet.java

@@ -0,0 +1,62 @@
+/*
+ * MIT License
+ *
+ * Copyright (c) 2017-2023 Ilkka Seppälä
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in all
+ * copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+ * SOFTWARE.
+ */
+
+package array;
+
+/**
+ * ReverseArraySnippet.
+ */
+public class ReverseArraySnippet {
+
+  /**
+   * The function then reverses the elements of the array between the starting and ending
+   * indices using a while loop and a temporary variable `temp`. Finally, the function returns
+   * the reversed array.
+   *
+   * @param array a array
+   * @param start start index array
+   * @param end end index array
+   * @return reverses elements in the array
+   * @throws IllegalArgumentException if the [start] index is greater
+   *         than the [end] index or if the array is null
+   **/
+  public static <T> T[] reverseArray(T[] array, int start, int end) {
+    if (start > end || array == null) {
+      throw new
+              IllegalArgumentException("Invalid argument!");
+    }
+    int minimumSizeArrayForReversal = 2;
+    if (start == end || array.length < minimumSizeArrayForReversal) {
+      return array;
+    }
+    while (start < end) {
+      T temp = array[start];
+      array[start] = array[end];
+      array[end] = temp;
+      start++;
+      end--;
+    }
+    return array;
+  }
+}

src/test/java/array/ReverseArrayTest.java

@@ -0,0 +1,137 @@
+/*
+ * MIT License
+ *
+ * Copyright (c) 2017-2023 Ilkka Seppälä
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in all
+ * copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+ * SOFTWARE.
+ */
+
+package array;
+
+import static org.junit.jupiter.api.Assertions.assertArrayEquals;
+import static org.junit.jupiter.api.Assertions.assertThrows;
+
+import org.junit.jupiter.api.Test;
+
+
+/**
+ * Tests for {@link ReverseArraySnippet#reverseArray(Object[], int, int)}}.
+ */
+
+class ReverseArrayTest {
+
+
+  /** reverseArray should correctly reverse the entire array. **/
+
+  @Test
+  void testReverseArrayFull() {
+    Integer[] arr = {1, 2, 3, 4, 5};
+    Integer[] result = ReverseArraySnippet.reverseArray(arr, 0, arr.length - 1);
+    Integer[] expected = {5, 4, 3, 2, 1};
+    assertArrayEquals(expected, result);
+  }
+
+  /** reverseArray should correctly reverse a subset of the array. **/
+
+  @Test
+  void testReverseArrayPartial() {
+    String[] arr = {"Ali", "Shabnam", "Reza", "Fatemeh"};
+    String[] result = ReverseArraySnippet.reverseArray(arr, 1, 2);
+    String[] expected = {"Ali", "Reza", "Shabnam", "Fatemeh"};
+    assertArrayEquals(expected, result);
+  }
+
+  /** reverseArray should correctly reverse a subset of the array with decimal values. **/
+
+  @Test
+  void testReverseArrayDecimal() {
+    Double[] arr = {5.5, 4.4, 3.3, 2.2, 1.1};
+    Double[] result = ReverseArraySnippet.reverseArray(arr, 2, 4);
+    Double[] expected = {5.5, 4.4, 1.1, 2.2, 3.3};
+    assertArrayEquals(expected, result);
+  }
+
+  /** reverseArray should correctly handle a single element array. **/
+
+  @Test
+  void testReverseArraySingleElement() {
+    Integer[] arr = {1};
+    Integer[] result = ReverseArraySnippet.reverseArray(arr, 0, arr.length - 1);
+    Integer[] expected = {1};
+    assertArrayEquals(expected, result);
+  }
+
+  /** reverseArray should correctly handle an empty array. **/
+
+  @Test
+  void testReverseArrayEmpty() {
+    Integer[] arr = new Integer[0];
+    Integer[] result = ReverseArraySnippet.reverseArray(arr, 0, 0);
+    Integer[] expected = new Integer[0];
+    assertArrayEquals(expected, result);
+  }
+
+  /** reverseArray when start and end are equal. **/
+
+  @Test
+  void testReverseArrayNoChange() {
+    Integer[] array = {1, 2, 3, 4, 5};
+    int start = 2;
+    int end = 2;
+    Integer[] reversedArray = ReverseArraySnippet.reverseArray(array, start, end);
+    assertArrayEquals(array, reversedArray);
+  }
+
+  /** reverseArray should throw ArrayIndexOutOfBoundsException if startIndex is less than 0. **/
+
+  @Test
+  void testReverseArrayNegativeStartIndex() {
+    Integer[] arr = {1, 2, 3, 4, 5};
+    assertThrows(ArrayIndexOutOfBoundsException.class, () ->
+            ReverseArraySnippet.reverseArray(arr, -1, 3));
+  }
+
+  /** reverseArray should throw ArrayIndexOutOfBoundsException if endIndex
+  *  is greater than the array size minus 1. **/
+
+  @Test
+  void testReverseArrayEndIndexOutOfBounds() {
+    Integer[] arr = {1, 2, 3, 4, 5};
+    assertThrows(ArrayIndexOutOfBoundsException.class,
+            () -> ReverseArraySnippet.reverseArray(arr, 2, 5));
+  }
+
+  /** reverseArray should throw ArrayIndexOutOfBoundsException
+  * if startIndex is greater than endIndex. **/
+
+  @Test
+  void testReverseArrayInvalidIndexes() {
+    Integer[] arr = {1, 2, 3, 4, 5};
+    assertThrows(IllegalArgumentException.class, () -> ReverseArraySnippet.reverseArray(arr, 3, 2));
+  }
+
+  /** reverseArray should throw IllegalArgumentException if the input array is null. */
+
+  @Test
+  void  testReverseArrayNullInput() {
+    assertThrows(IllegalArgumentException.class, () ->
+            ReverseArraySnippet.reverseArray(null, 0, 2));
+  }
+
+}