java8flatMap方法的妙用
import java.util.Arrays; import java.util.List; import static java.util.stream.Collectors.toList; public class Test { public static void main(String[] args) { List<Integer> numbers1 = Arrays.asList(1, 2, 3); List<Integer> numbers2 = Arrays.asList(3, 4); //[(1, 3), (1, 4), (2, 3), (2, 4), (3, 3), (3, 4)] List<int[]> pairs = numbers1.stream().flatMap(i -> numbers2.stream().map(j -> new int[]{i, j})).collect(toList()); //[(2, 4), (3, 3)] List<int[]> collect = numbers1.stream().flatMap(i -> numbers2.stream().filter(j -> (i + j) % 3 == 0).map(j -> new int[]{i, j})).collect(toList()); for (int[] ints : collect) { System.out.println(Arrays.toString(ints)); } } }