Remove duplicates in unordered array with Java using streams

Heres how to remove duplicates from an unordered primitive int array on Java using streams.

You can find the complete code for this here: remove_dupes_unordered_the_smart_way.jsh.

Consider the following straight forward problem, you receive a primitive int array and you need to return a new array only containing the unique elements.

Because we are using streams since 2014 and we know that a Set does not accept duplicates, we only need to collect the array into a set and back into an array.

int[] removeDupes(int arr[]) {
    return Arrays.stream(arr)
        .boxed()
        .collect(Collectors.toSet()).stream()
        .mapToInt(Integer::intValue).toArray();
}

The boxed method just returns an Integer stream instead of a primitive one.

Download the complete code from this post here: remove_dupes_unordered_the_smart_way.jsh.

Comments

[Wellington Domiciano]

This nice!

There is another even simpler way using distinct():

int[] removeDupesWithDistinct(int[] arr) {
  return Arrays.stream(arr).distinct().toArray();
}