Java20-HashMap

 

 

 

package doudou;

import java.util.HashMap;

import com.alibaba.fastjson.JSONObject;

public class test_hashMap {
    public static void main(String[] args) {
        HashMap<String,Integer>hm=new HashMap<>();
        System.out.println("------------java.util.HashMap----------------");
        //新增
        hm.put("张三", 12);
        hm.put("王五", 12);
        hm.put("clover", 22);
        hm.put("dou",333);
        hm.put("刘一", 1);
        System.out.println("hm:"+hm);
        //判断
        if (hm.equals("clover")){

           System.out.println("存在clover");
        }
       //移除
        hm.remove("clover");
        System.out.println("clover已经被移除:"+hm);
        //查看大小
        int a=hm.size();
        System.out.println("字典的长度为:"+a);
        //变成string
        String b=hm.toString();
        System.out.println("toString方法:"+b);
        //替换
        hm.replace("刘一", 999);
        System.out.println("replace方法:"+hm);
        //查询
        Integer c=hm.get("刘一");
        System.out.println("key为刘一的新对应的value是:"+c);
        //判断字典是否为空
        if(hm.isEmpty()){
            System.out.println("字典为空");
        }
        else{
            System.out.println("字典不为空");
        }
        //清空字典
        hm.clear();
        System.out.println("清空后的字典为:"+hm);
       
        System.out.println("------------com.alibaba.fastjson.JSONObject------------");
        JSONObject result = new JSONObject();
        result.put("json", 111);
        result.put("json", 111);
        result.put("json1", 111);
        result.put("json", 1112);
        System.out.println("fastjson练习："+result);
        System.out.println(result.getClass());
        
    
        
   }

}