Iterate And Filter Array 2D Java 8

Question

I have an Array like so:

int[] array_example = {0, 1, 2, 3, 4, 5, 6, 7, 8, 9};
Long count_array = Arrays.stream(array_example)
                      .filter(x -> x>5)
                      .count();

and a 2d array like so:

int[][] matrix_example = {{0, 1, 2, 3, 4}, {5, 6, 7, 8, 9}};
Long count_matrix = 0L;
for(int[] temp: matrix_example){
    for(int x_y: temp){
        if(x_y > 5)
           count_matrix++;
    }
}

How could I obtain the number of elements greater than x of a matrix with java 8 or higher?

Naman · Accepted Answer · 2018-12-21 06:03:16Z

4

You can create an IntStream of the matrix using flatMapToInt then use filter and count as earlier :

Long count_matrix = Arrays.stream(matrix_example) // Stream<int[]>
        .flatMapToInt(Arrays::stream) // IntStream
        .filter(x_y -> x_y > 5) // filtered as per your 'if'
        .count(); // count of such elements

edited Dec 21, 2018 at 6:03

answered Dec 21, 2018 at 5:55

Naman

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Comments

Ousmane D. · Accepted Answer · 2018-12-21 08:05:33Z

1

Here's one way to go about it:

long count = Arrays.stream(matrix_example)
                   .mapToLong(a -> Arrays.stream(a).filter(x -> x > 5).count()).sum();

creates a stream from matrix_example via Arrays.stream
maps each array to the number of times a given element is greater than 5 via mapToLong
then we take all those amounts and sum them up to get the count via sum

answered Dec 21, 2018 at 8:05

Ousmane D.

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