Question

 public class Java_03 {
 public static void main(String[] args) {
    List<Integer> listOfEven = Stream.iterate(1, i -> i+1)
                                    .filter(i -> i % 2 == 0)
                                    .limit(10)
                                    .collect(Collectors.toList());
    List<Integer> listOf3 = Stream.iterate(1, i -> i+1)
                                    .filter(i -> i % 3 == 0)
                                    .limit(10)
                                    .collect(Collectors.toList());

    // how to rewrite this code using lambdas and streams ?
    Map<Integer, Integer> map = new TreeMap<>();
    int i = 0;
    for (int a : listOf3) {
        map.put(listOfEven.get(i), a);
        i++;
    }
    System.out.println(map);
 } 
}

我想用lambdas和stream编写这段代码我尝试了很多但是失败了。请帮忙。

map应该包含：key - 乘法表2和value - 乘法表3 例如 - {2 = 3,4 = 6,6 = 9,8 = 12,10 = 15,12 = 18,14 = 21,16 = 24,18 = 27,20 = 30}

Answer 1

方法Collectors.toMap可用于执行请求。

示例（计数保持计数器）： -

int[] count = {0};

listOf3.stream().collect(Collectors.toMap(x->listOfEven.get(count[0]++), x->x))

运行示例： -

public static void main(String[] args) {
        List<Integer> listOfEven = Stream.iterate(1, i -> i+1)
                                        .filter(i -> i % 2 == 0)
                                        .limit(10)
                                        .collect(Collectors.toList());
        List<Integer> listOf3 = Stream.iterate(1, i -> i+1)
                                        .filter(i -> i % 3 == 0)
                                        .limit(10)
                                        .collect(Collectors.toList());

         int[] count = {0};
         System.out.println(listOf3.stream().collect(Collectors.toMap(x->listOfEven.get(count[0]++), x->x)));
         }

Answer 2

IntStream.range(0, listOf3.size()).forEach(i -> map.put(listOfEven.get(i), listOf3.get(i)));

如何使用lambdas和stream重写这段代码？

2 个答案: