类集框架Map

package su;

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

public class Test{
    public static void main(String args[]){
        Map<Integer , String> map = new HashMap<Integer , String>();
        map.put(1, "a");
        map.put(2, "a");//value的值可以重复
        map.put(3, "s");
        map.put(4, "y");
        map.put(2, "c");//KEY重复会导致value覆盖
        System.out.println(map.get(1));
        System.out.println(map.get(2));
    }
}