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提示：以下是本篇文章正文内容，下面案例可供参考

一、Map的实现类的结构

二、Map结构的理解

三、HashMap的底层实现原理? 以jdk7的说明:

四、Map中定义的方法

五、总结：常用方法

六、代码

package com.tyust.edu;

import org.junit.Test;

import java.util.*;

/**
 * @author YML TYUST-XDU 2019-2026
 * @create 2023-10-12 8:45
 */
public class MapTest {

    @Test
    public void test1(){
        Map map = new HashMap();

//       map = new Hashtable();

        map.put(null,null);
    }

    @Test
    public void test3() {
        Map map = new HashMap();
        //添加
        map.put("AA",123);
        map.put(45,123);
        map.put("nn",23);
        //修改
        map.put("AA",37);

        System.out.println(map);

        Map map1 = new HashMap();
        map1.put("CC",123);
        map1.put("DD",123);

        map.putAll(map1);
        System.out.println(map);

        Object value = map.remove("CC");
        System.out.println(value);
        System.out.println(map);

        map.clear();
        System.out.println(map.size());

    }

    @Test
    public void test4() {
        Map map = new HashMap();
        //添加
        map.put("AA", 123);
        map.put(45, 123);
        map.put("nn", 23);
        //修改
        map.put("AA", 37);

        System.out.println(map.get(45));
        boolean isExit = map.containsKey("nn");
        System.out.println(isExit);

        isExit = map.containsValue(123);
        System.out.println(isExit);
        map.clear();
        System.out.println(map.isEmpty());
    }

    @Test
    public void test5() {
        Map map = new HashMap();
        //添加
        map.put("AA", 123);
        map.put(45, 123);
        map.put("nn", 23);
        //修改
        map.put("AA", 37);


        //遍历所有的key集keySet()
        Set set = map.keySet();
        Iterator iterator = set.iterator();
        while(iterator.hasNext()){
            System.out.println(iterator.next());
        }

        //遍历所有的value集：values()
        Collection values = map.values();
        for(Object obj:values){
            System.out.println(obj);
        }


        System.out.println();
        //遍历所有的key-value
        //entrySet()
        Set entrySet = map.entrySet();
        Iterator iterator1 = entrySet.iterator();
        while(iterator1.hasNext()){
            Object obj = iterator1.next();
            //entrySet集合中的元素都是entry
            Map.Entry entry = (Map.Entry)obj;
            System.out.println(entry.getKey()+"--->"+entry.getValue());
        }


        System.out.println();
        Set keySet = map.keySet();
        Iterator iterator2 = keySet.iterator();
        while(iterator2.hasNext()){
            //System.out.println(iterator2.next());
            Object key = iterator2.next();
            Object value = map.get(key);
            System.out.println(key+"--->"+value);
        }


    }


}