Question

我有一个MyModel班级和一个List<MyModel>

public static class MyModel{
    private int left;
    private int right;
    private int state = 0;
    public MyModel(int left, int right, int state){
        this.left = left;
        this.right = right;
        this.state = state;
    }
    public int getLeft() {
        return left;
    }
    public void setLeft(int left) {
        this.left = left;
    }
    public int getRight() {
        return right;
    }
    public void setRight(int right) {
        this.right = right;
    }
    public int getState() {
        return state;
    }
    public void setState(int state) {
        this.state = state;
    }
}

我希望制作，MyModel会映射1或2个整数值（左，右或两者）

我可以做1但不知道怎么做2

这就是我目前的做法：

List<MyModel> models = new ArrayList<MyModel>();
models.add(new MyModel(1, 2, 1));
models.add(new MyModel(3, 4, 2));
models.add(new MyModel(5, 6, 3));
List<Integer> result = models.stream().map(p -> {
    switch (p.getState()) {
    case 1:
        return p.getLeft();
    case 2:
        return p.getRight();
    case 3:
        //Problem here i need add left and right into result list 
    default:
        return p.getLeft();             
    }
}).collect(Collectors.toList());

Answer 1

使用flatMap，它完全符合您的需要：

List<Integer> result = models.stream().flatMap(p -> {
    switch (p.getState()) {
    case 1:
        return Stream.of(p.getLeft());
    case 2:
        return Stream.of(p.getRight());
    case 3:
        return Stream.of(p.getLeft(), p.getRight());
    default:
        return Stream.of(p.getLeft());
        // you can also return Stream.empty() if appropriate
    }
}).collect(Collectors.toList());

Answer 2

您可以使用Collector API：

sort

如何在java流中映射1-1以上的记录？

2 个答案: