1、问题描述

小明正在设计一个简单的多人聊天室系统，有多个用户和一个聊天室中介者，用户通过中介者进行聊天，请你帮他完成这个系统的设计。

输入示例
3
User1 User2 User3
User1 Hello_All!
User2 Hi_User1!
User3 How_is_everyone?

输出示例
User2 received: Hello_All!
User3 received: Hello_All!
User1 received: Hi_User1!
User3 received: Hi_User1!
User1 received: How_is_everyone?
User2 received: How_is_everyone?

2、中间者模式

作者认为的核心理念
中间者：持有所有代理，负责发送和接收代理的信息(包含两个方法)
代理：包含中间者引用，消息都是发送给中间者，中间者再掉用自己的发送信息方法

3、代码

import com.sun.java.accessibility.util.TopLevelWindowListener;import java.util.*;public class Main{public static void main(String[] args){Scanner sc=new Scanner(System.in);int number=sc.nextInt();sc.nextLine();Platform p=new QQ();String s=sc.nextLine();String[] names=s.split(" ");for(int i=0;i<number;i++){User u=new User(p,names[i]);p.register(u);p.register(u);}while(sc.hasNextLine()){String input=sc.nextLine();if(input.isEmpty()){break;}String[] inputs=input.split(" ");User u=p.getUser(inputs[0]);u.send(inputs[1]);}}
}interface Platform{void register(User u);void send(String message,User u);User getUser(String userName);
}class QQ implements Platform{private Map<String,User> hashMap;public QQ(){this.hashMap=new LinkedHashMap<>();}@Overridepublic void register(User u) {this.hashMap.put(u.getUserName(),u);}@Overridepublic void send(String message, User u) {for(User tmp:this.hashMap.values()){if(!tmp.getUserName().equals(u.getUserName())){tmp.receive(message);}}}@Overridepublic User getUser(String userName) {return hashMap.get(userName)==null?null:hashMap.get(userName);}
}interface Agent{void send(String message);void receive(String message);
}class User implements Agent{private Platform qq;private String name;public User(Platform p,String userName){this.qq=p;this.name=userName;}public String getUserName(){return this.name;}@Overridepublic void send(String message) {qq.send(message,this);}@Overridepublic void receive(String message) {System.out.println(this.name+" received: "+message);}
}