HashMap的常用方法

package ditu.com;

import java.util.Collection;
import java.util.HashMap;
import java.util.Map;
import java.util.Map.Entry;
import java.util.Set;

public class TestMap {

    public static void main(String[] args) {
    //向Map中插入5个人名
        Map <Integer,String>map=new HashMap <Integer,String>();
        map.put(1,"张飞");
        map.put(6,"刘备");
        map.put(4,"关羽");
        map.put(2,"钟馗");
        map.put(3,"达摩");

        Map <Integer,String>map2=new HashMap <Integer,String>();
        map.put(4,"孙尚香");
        map.put(7,"孙悟空");

        map.putAll(map2);
        System.out.println(map.get(4));
//以上是map的基本操作
//如何遍历map中所有元素？

        //1.先获得键的集合
    Set <Integer>set=map.keySet();
        for(Integer i:set){
            System.out.println(i+":"+map.get(i));
        }

    //2.只获得值(用的比较少)
        Collection<String>c=map.values();
        for(String cc:c){
            System.out.println(cc);
        }
//最难理解但效率最高。获得键值对的封装体，Map.Entry
    Set<Entry<Integer,String>>s=map.entrySet();
        for(Entry<Integer,String> e:s){
            System.out.println(e.getKey()+":"+e.getValue());
        }

    }

}