Map中整合全部相同value值的key值

package com.atguigu.mvc.bean;

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


public class main {
    public static void main(String[] args) {
        Map friends_Name = new HashMap();
        friends_Name.put("x", "y");
        friends_Name.put("a", "b");
        friends_Name.put("c", "d");
        friends_Name.put("e", "d");
        friends_Name.put("f", "b");
        friends_Name.put("m", "n");

        Map> friends_Name2 = new HashMap>();
        String entryName = null;
        String entryFriends = null;
        ArrayList FriendsList = new ArrayList();
        ArrayList FriendsList2 = new ArrayList();

        for (Map.Entry entry : friends_Name.entrySet()) {
            FriendsList.clear();
            FriendsList2.clear();
            entryFriends = entry.getKey();
            entryName = entry.getValue();

            if (friends_Name2.keySet().contains(entryName)) {
                FriendsList2 = friends_Name2.get(entryName);
                FriendsList2.add(entryFriends);
                friends_Name2.put(entryName, (ArrayList) FriendsList2.clone());
            } else {
                FriendsList.add(entryFriends);
                friends_Name2.put(entryName, (ArrayList) FriendsList.clone());
            }
        }
        System.out.println(friends_Name2);
    }
}