元组置换

Question

假设我有一个元组(1,2)。我想创建一个流，它给出元组值的所有可能组合。所以我想创建一个流，它看起来如下所示：

[(1, 1), (1, 2), (2, 1), (2, 2)]

这是我的元组的类：

public class Tuple<T> {
    private final T first;
    private final T second;

    public Tuple(T first, T second) {
        assert first != null;
        assert second != null;

        this.first = first;
        this.second = second;
    }

    public T getFirst() {
        return first;
    }

    public T getSecond() {
        return second;
    }

    @Override
    ...

这是我的元组集的类：

public class TupleSet<T> implements Set<Tuple<T>> {
    private Set<T> set;
    public TupleSet(Set<T> set) {
        this.set = set;
        //This is where I want to create my tuple-set
    }
   
    public Stream<Tuple<T>> getElements() {
    return; //This is where I want to return a stream of that tuple-set
}

我如何使用置换获得我想要的元组集？

Answer 1

强力解决方案是以嵌套方式迭代set set 并应用flatmap来创建 > :

public Stream<Tuple<T>> getElements() {
    return set.stream()
            .flatMap(first -> set.stream()
                    .map(second -> new Tuple(first, second)));
}