Java Collection - 如何在地图中按键删除

import java.util.HashMap;
import java.util.Map;

public class Main {

    public static void main(String[] args) {
        Map<Integer, String> map = new HashMap<>();

        for (int i = 0; i < 10; i++) {
            map.putIfAbsent(i, "val" + i);
        }

        map.forEach((id, val) -> System.out.println(val));

        map.remove(3, "val3");
        System.out.println(map.get(3));             // val33

        map.remove(3, "val33");
        System.out.println(map.get(3));             // null
    }

}