Java返回嵌套类型参数

public class Example {
    public static <T, U> Pair<T, U> getNestedPair(T first, U second) {
        return new Pair<>(first, second);
    }

    public static void main(String[] args) {
        Pair<String, Pair<Integer, Double>> nestedPair = getNestedPair("Hello", new Pair<>(42, 3.14));
        System.out.println(nestedPair.getFirst());
        System.out.println(nestedPair.getSecond().getFirst());
        System.out.println(nestedPair.getSecond().getSecond());
    }
}

class Pair<T, U> {
    private T first;
    private U second;

    public Pair(T first, U second) {
        this.first = first;
        this.second = second;
    }

    public T getFirst() {
        return first;
    }

    public U getSecond() {
        return second;
    }
}