Java Map 练习

package com.test;

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

public class HashMapTest {
	public static void main(String[] args) {
		map3();
	}
	
	public static void map1(){
		Map<String,String> map = new HashMap<String,String>();
		map.put("1", "A");
		map.put("2", "B");
		map.put("3", "C");
		map.put("4", "D");
		map.put("5", "E");
		
		//通过Map.entrySet()使用iterator()遍历key和value  
		Iterator<Entry<String, String>> iterator = map.entrySet().iterator();
		while(iterator.hasNext()){
			Map.Entry<String, String> n = iterator.next();
			System.out.println("Key:"+n.getKey()+"\t"+"Value:"+n.getValue());
		}
	}
	
	public static void map2(){
		Map<String,String> map = new HashMap<String,String>();
		map.put("1", "A");
		map.put("2", "B");
		map.put("3", "C");
		map.put("4", "D");
		map.put("5", "E");
		
        //通过Map.keySet()遍历key和value  
        //这里有一个二次取值的过程,所以并不推荐  
		for(String s:map.keySet()){
			System.out.println("Key:"+s+"\t"+"Value:"+map.get(s));	
		}
	}
	
	public static void map3(){
		Map<String,String> map = new HashMap<String,String>();
		map.put("1", "A");
		map.put("2", "B");
		map.put("3", "C");
		map.put("4", "D");
		map.put("5", "E");
		
        //第三种:通过Map.entrySet()遍历key和value  
        //JDK1.5后的遍历形式,代码看起来比较整洁,更推荐采用  
		for(Map.Entry<String, String> m:map.entrySet()){
			System.out.println("Key:"+m.getKey()+"\t"+"Value:"+m.getValue());	
		}
	}
}