How to reverse an array in Java?

March 18, 2022

To reverse an array in Java, turn the array into a List, then do Collections.reverse, finally convert back to array with list.toArray.

Here's how you do it:

String[] array = new String[] { "A", "B", "C" };
java.util.List<String> listFromArray = java.util.Arrays.asList(array);
java.util.Collections.reverse(listFromArray);
String[] reversedArray = listFromArray.toArray(String[]::new);

System.out.println(java.util.Arrays.toString(reversedArray)); // [C, B, A]

Primitive arrays

Here's how you do it if your array is int[]:

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

for (int i = 0; i < array.length / 2; i++) {
  int item = array[i];
  array[i] = array[array.length - i - 1];
  array[array.length - i - 1] = item;
}

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

Here's how you do it if your array is double[]:

double[] array = new double[] { 1.0, 2.0, 3.0 };

for (int i = 0; i < array.length / 2; i++) {
  double item = array[i];
  array[i] = array[array.length - i - 1];
  array[array.length - i - 1] = item;
}

System.out.println(java.util.Arrays.toString(array)); // [3.0, 2.0, 1.0]