Rotating an array by a given number of positions.

Here’s an example program in Java that rotates an array by a given number of positions:

  import java.util.Arrays;

  public class ArrayRotation {

    public static void main(String[] args) {

        int[] arr = {1, 2, 3, 4, 5};

        int rotations = 2;

        System.out.println("Original array: " + Arrays.toString(arr));

        rotateArray(arr, rotations);

        System.out.println("Rotated array: " + Arrays.toString(arr));

    }

    public static void rotateArray(int[] arr, int rotations) {

        int length = arr.length;

        // Normalize the number of rotations

        rotations = rotations % length;

        // Reverse the entire array

        reverseArray(arr, 0, length - 1);

        // Reverse the first part of the array

        reverseArray(arr, 0, rotations - 1);

        // Reverse the second part of the array

        reverseArray(arr, rotations, length - 1);

    }

    public static void reverseArray(int[] arr, int start, int end) {

        while (start < end) {

            int temp = arr[start];

            arr[start] = arr[end];

            arr[end] = temp;

            start++;

            end--;
        }
    }
}

In this program, we define an array `arr` and the number of rotations `rotations` that we want to perform. The `rotateArray` method is responsible for rotating the array, while the `reverseArray` method is used to reverse a portion of the array.

The program first prints the original array, performs the rotation, and then prints the rotated array. In this example, the original array is `[1, 2, 3, 4, 5]`, and we rotate it by 2 positions. The expected output will be:

Original array: [1, 2, 3, 4, 5]

Rotated array: [4, 5, 1, 2, 3]

The rotation is done in-place, meaning it modifies the original array rather than creating a new array.