Compare two integer arrays using Java Stream

Question

I have two integer arrays eg -

int[] a = {2, 7, 9}

int[] b = {4, 2, 8}

I want to compare it element by element ie 2 to 4 then 7 to 2 and finally 9 to 8 . Each comparison result will be stored in a list.

This is pretty easy to do in the traditional Java ways. But I want to use Stream here. Any pointers?

Answer 1

You may do it like so,

List<Boolean> equalityResult = IntStream.range(0, a.length).mapToObj(i -> a[i] == b[i])
                .collect(Collectors.toList());

Precondition: both the arrays are of same size.

Answer 2

Assuming the length of both the input arrays are same

List<Integer> list = IntStream.range(0, a.length).mapToObj(i -> Integer.compare(a[i], b[i]))
            .collect(Collectors.toCollection(() -> new ArrayList<>(a.length)));

Answer 3

Same as other answers with a bit difference

List<Integer> result = IntStream.rangeClosed(0,a.length-1)
            .boxed()
            .map(i->Integer.compare(a[i],b[i]))
            .collect(Collectors.toList());

Answer 4

You're essentially looking for the functionality of a Zip operation (which is not available in Java yet).

To get a set of booleans, as a result, I would recommend:

boolean[] accumulator = new boolean[a.length];
IntStream.range(0, a.length)
         .forEachOrdered(i -> accumulator[i] = a[i] == b[i]);

and respectively to get the result as an int between corresponding elements in both arrays:

int[] ints = IntStream.range(0, a.length)
                      .map(i -> Integer.compare(a[i], b[i]))
                      .toArray();