How do I reverse an int array in Java?

With Commons.Lang, you could simply use

ArrayUtils.reverse(int[] array)

Most of the time, it's quicker and more bug-safe to stick with easily available libraries already unit-tested and user-tested when they take care of your problem.

To reverse an int array, you swap items up until you reach the midpoint, like this:

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

The way you are doing it, you swap each element twice, so the result is the same as the initial list.

Collections.reverse(Arrays.asList(yourArray));

java.util.Collections.reverse() can reverse java.util.Lists and java.util.Arrays.asList() returns a list that wraps the the specific array you pass to it, therefore yourArray is reversed after the invocation of Collections.reverse().

The cost is just the creation of one List-object and no additional libraries are required.

A similar solution has been presented in the answer of Tarik and their commentors, but I think this answer would be more concise and more easily parsable.