How do I reverse an int array in Java?

To reverse an int array in Java, you can use a loop to swap the elements at the beginning and end of the array, and then move the pointers inward until they meet in the middle of the array.

Here is an example of how you can do this:

import java.util.Arrays;

int[] array = {1, 2, 3, 4, 5};

int left = 0;
int right = array.length - 1;

while (left < right) {
  // swap the elements at the left and right indices
  int temp = array[left];
  array[left] = array[right];
  array[right] = temp;

  // move the pointers inward
  left++;
  right--;
}

System.out.println(Arrays.toString(array)); // [5, 4, 3, 2, 1]

This approach runs in O(n) time and O(1) space.

Alternatively, you can use the Collections.reverse method to reverse the elements of an int array that has been converted to a List.

Here is an example of how you can do this:

import java.util.Arrays;
import java.util.Collections;
import java.util.List;
import java.util.stream.Collectors;

int[] array = {1, 2, 3, 4, 5};
List<Integer> list = Arrays.stream(array).boxed().collect(Collectors.toList());

Collections.reverse(list);

int[] reversedArray = list.stream().mapToInt(i -> i).toArray();
System.out.println(Arrays.toString(reversedArray)); // [5, 4, 3, 2, 1]

This approach also runs in O(n) time but uses O(n) space due to the intermediate List and boxing overhead.