Sum two arrays element-by-element in Java

Question

What is the easiest way to sum two arrays element-by-element?

I know that you can use a for loop such as the following:

int[] a = {0, 1, 2};
int[] b = {3, 4, 5};
int[] c = new int[a.length];
for (int i = 0; i < a.length; ++i) {
    c[i] = a[i] + b[i];
}

But in languages such as MATLAB, you can do the element-by-element array sum by just writing c = a + b. Is there an easy way to do this in Java?

The method that comes to mind is using the RealVector class from Apache Commons Math, but that method is rather verbose.

Answer 1

There's certainly nothing to enable this in the language. I don't know of anything in the standard libraries either, but it's trivial to put the code you've written into a utility method which you can call from anywhere you need it.

Answer 2

One more answer, using streams and providing a more generic solution:

import org.junit.Assert;
import org.junit.Test;

import java.util.function.IntBinaryOperator;
import java.util.stream.IntStream;

public class SOTest {

    @Test
    public void test() {
        int[] a = {0, 1, 2};
        int[] b = {3, 4, 5};

        int[] sum = applyOn2Arrays((x, y) -> x + y, a, b);
        int[] diff = applyOn2Arrays((x, y) -> x - y, a, b);
        int[] mult = applyOn2Arrays((x, y) -> x * y, a, b);


        Assert.assertArrayEquals(new int [] {3,5,7}, sum);
        Assert.assertArrayEquals(new int [] {-3,-3,-3}, diff);
        Assert.assertArrayEquals(new int [] {0,4,10}, mult);
    }

    private int[] applyOn2Arrays(IntBinaryOperator operator, int[] a, int b[]) {
        return IntStream.range(0, a.length)
                .map(index -> operator.applyAsInt(a[index], b[index]))
                .toArray();
    }
}