map

map中常用的方法

put（k，v）；添加值

package com.example.demo.controller;

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

public class MapTesy {
    public static void main(String[] args) {
        Map map = new HashMap();
        Map map1 = new HashMap();
        map.put("1","我");
        map.put(2,5);
        System.out.println(map);
        System.out.println(map1);
        map1.put(3,465);
        map1.put(4,456);
        map.putAll(map1);
        System.out.println(map);
        System.out.println(map1);
        map1.clear();
        System.out.println(map1);
        System.out.println(map.containsKey("1"));
        System.out.println(map.containsKey(2));
    }
}

putAll（map）；添加map集合

clear（）；清楚集合

containsKey（）；是否包含主键