这是IntStream嵌套循环的最佳选择吗？错误是什么？

Question

I want to create a triple nested iteration of numbers from 0 to 500, stepping by 10.

I tried the following and I get an error on the closing round brackets. Can you please advise?

Thank you.

public class App {
    public static void main(String[] args) {

        IntStream.rangeClosed(0, 500).filter(a -> a % 10 == 0).forEach( a ->
                IntStream.rangeClosed(0, 500).filter(b -> b % 10 == 0).forEach( b ->
                        IntStream.rangeClosed(0, 500).filter(c -> c % 10 == 0).forEach( c->
                                System.out.println(a + ", " + b + ", " + c);
                        );
                );
        );
    }
}

Answer 1

Instead of generating 501 elements in each stream and then filtering all the elements not divisible by 10, you can generate IntStream s that contain only multiples of 10:

IntStream.iterate(0, i->i+10).limit(51).forEach( a ->
            IntStream.iterate(0, i->i+10).limit(51).forEach( b ->
                    IntStream.iterate(0, i->i+10).limit(51).forEach( c->
                            System.out.println(a + ", " + b + ", " + c)
                    )
            )
);

Answer 2

My suggestion is:

    IntStream.rangeClosed(0, 50)
            .forEach(a -> IntStream.rangeClosed(0, 50)
                    .forEach(b -> IntStream.rangeClosed(0, 50)
                            .forEach(c -> System.out.format("%3d, %3d, %3d%n",
                                    a * 10, b * 10, c * 10))));

Excerpt from output:

  0,   0,   0
  0,   0,  10
  0,   0,  20
  0,   0,  30
  0,   0,  40

…
500, 500, 490
500, 500, 500

The limit(51) in Eran's answer looks a little bit funny.

What went wrong in your code? As Eran said in a comment , you cannot have semicolon, ; , after method invocations inside your stream (unless surrounded by curly braces). Just remove the first three semicolons, and your code works.