Map集合的遍历方式

1.通过Map.keySet遍历key和value
map.keySet()返回的是所有key的值
map.get(in)得到每个key对应value的值
2.通过Map.keySet使用iterator遍历key和value
方法同上
3.通过Map.entrySet遍历key和value
map.entrySet() 返回此映射中包含的映射关系的 Set视图。
4.通过Map.entrySet使用iterator遍历key和value
方法同上

import java.util.HashMap;
import java.util.Iterator;
import java.util.Map;
import java.util.Set;

public class MapTest {
    public static void main(String[] args) {
       MapBianli1();
       MapBianli2();
       MapBianli3();
       MapBianli4();
    }

    /**
     * 获取keySet，得到一个个的key
     * map.get()获取key所对应的value
     * 
     */
    public static void MapBianli1(){
        Map<String,String> map = new HashMap<String, String>();
        map.put("name","马云");
        map.put("age","28");
        map.put("gender","男");
        map.put("major","电子商务");
        System.out.println("方法一");
        for(String key:map.keySet()){
            System.out.println(key+":  "+map.get(key) );
        }
    }

    /**
     * 获取entrySet，entrySet装的是一个个键值对
     * entrySet.getKey获取key，entrySet.getValue获取value
     */
    public static void MapBianli2(){
        Map<String,String> map = new HashMap<String, String>();
        map.put("name","马云");
        map.put("age","28");
        map.put("gender","男");
        map.put("major","电子商务");
        System.out.println("方法二");
        Set<Map.Entry<String, String>> entrySet = map.entrySet();
        for (Map.Entry<String, String> entry : entrySet) {
            System.out.println(entry.getKey()+":  "+entry.getValue());
        }
        
    }

    /**
     *利用迭代器遍历重复keySet的遍历方法
     */
    public static void MapBianli3(){
        Map<String,String> map = new HashMap<String, String>();
        map.put("name","马云");
        map.put("age","28");
        map.put("gender","男");
        map.put("major","电子商务");
        System.out.println("方法三");
        Iterator<String> iterator = map.keySet().iterator();
        while (iterator.hasNext()){
            String key = iterator.next();
            System.out.println(key+":  "+map.get(key));
        }
    }


    /**
     * 利用迭代器重复entrySet的遍历方法
     */
    public static void MapBianli4(){
        Map<String,String> map = new HashMap<String, String>();
        map.put("name","马云");
        map.put("age","28");
        map.put("gender","男");
        map.put("major","电子商务");
        System.out.println("方法四");
        Iterator<Map.Entry<String, String>> iterator = map.entrySet().iterator();
        while (iterator.hasNext()){
            Map.Entry<String, String> entry = iterator.next();
            System.out.println(entry.getKey()+":  "+entry.getValue());
        }
    }
}

 

来源：CSDN

作者：南方_少年

链接：https://blog.csdn.net/apache_ant/article/details/104114281