Java集合框架为程序员提供了预先包装的数据结构和算法来操纵他们。

[Bol5261]

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

public class S_Map {
    public static void main(String[] args){
        Map<String,String> map=new HashMap<String,String>();
        map.put("1","value1");
        map.put("2","value2");
        map.put("3","value3");

        //第一种：普遍使用，二次取值
        for(String key:map.keySet()){
            System.out.println("key="+key+" and value="+map.get(key));
        }

        //第二种
        Iterator<Map.Entry<String,String >> it=map.entrySet().iterator();
        while(it.hasNext()){
            Map.Entry<String,String> entry=it.next();
            System.out.println("key="+entry.getKey()+" and value="+entry.getValue());
        }

        //第三种：推荐，尤其是容量大时
        for(Map.Entry<String,String>entry:map.entrySet()){
            System.out.println("key="+entry.getKey()+" and value="+entry.getValue());
        }

        //第四种
        for(String v:map.values()){
            System.out.println("value="+v);
        }
    }
}



key=1 and value=value1
key=2 and value=value2
key=3 and value=value3
key=1 and value=value1
key=2 and value=value2
key=3 and value=value3
key=1 and value=value1
key=2 and value=value2
key=3 and value=value3
value=value1
value=value2
value=value3

Process finished with exit code 0