Stream from two dimensional array in java

Question

I am trying to get an IntStream out of an n dimensional int arrays. Is there a nice API way to do it? I know the concatenate method for two streams.

Answer 1

Assuming you want to process array of array sequentially in row-major approach, this should work:

int[][] arr = { {1, 2, 3}, {4, 5, 6}, {7, 8, 9} }; IntStream stream = Arrays.stream(arr).flatMapToInt(x -> Arrays.stream(x)); 

First it invokes the Arrays.stream(T[]) method, where T is inferred as int[], to get a Stream<int[]>, and then Stream#flatMapToInt() method maps each int[] element to an IntStream using Arrays.stream(int[]) method.

Answer 2

To further expand on Rohit's answer, a method reference can be used to slightly shorten the amount of code required:

int[][] arr = { {1, 2, 3},                  {4, 5, 6},                 {7, 8, 9} };  IntStream stream = Arrays.stream(arr).flatMapToInt(Arrays::stream);