泛型类型多态

public 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;
    }
}

Pair<Integer, String> pair = new Pair<>(1, "hello");

public static <T extends Comparable<T>> T max(T a, T b) {
    return a.compareTo(b) > 0 ? a : b;
}

int maxInt = max(1, 2);
String maxString = max("hello", "world");