中介者模式的核心逻辑就是解耦对象‘多对多’的相互依赖关系。当遇到一大堆混乱的对象呈现“网状结构”，利用通过中介者模式解耦对象之间的通讯。

代码案例

抽象中介类

public abstract class AbstractChatRoom {
    
    public abstract void notice(String message , User user); //声明notice方法

    public abstract void register(User user);
}

实现中介类

package com.example.dyc.mymedia;

import java.util.ArrayList;
import java.util.List;

public class ChatRoom extends AbstractChatRoom {  //继承AbstractChatRoom

    public List<User> users = new ArrayList<>();  //声明列表类存储User

    @Override
    public void register(User user){   //登录添加用户
        users.add(user);
    }

    @Override
    public void notice(String message,User user){  //notice方法的重写
        for(User u : users){   //遍历
            if(u != user){
                u.getMessage(message);
            }
        }
    }
}

User

package com.example.dyc.mymedia;

public abstract class User {   //抽象类

    protected AbstractChatRoom chatRoom;  //聊天室对象

    public User(AbstractChatRoom chatRoom){
        this.chatRoom = chatRoom;
        this.chatRoom.register(this);
    }

    public abstract void sendMessage(String msg);  //声明发送消息的方法
    public abstract void getMessage(String msg);   //声明接收消息的方法
}

UserA：

package com.example.dyc.mymedia;

//UserA
public class UserA extends User {

    private String userId;

    public UserA(String userId, AbstractChatRoom chatRoom) {
        super(chatRoom);
        this.userId = userId;
    }

    @Override
    public void sendMessage(String msg){
        System.out.println(userId + "发送 "+msg);
        chatRoom.notice(msg,this);
    }
    @Override
    public void getMessage(String msg){
        System.out.println(userId + "收到 "+msg );
    }
}

客户端

public class MyTest {
    public static void main(String[] args) {

        ChatRoom chatRoom = new ChatRoom();
        UserA userLi = new UserA("小李", chatRoom);
        UserA userWa = new UserA("小娃", chatRoom);

        userLi.sendMessage("我是小李");
        System.out.println("===================");
        userWa.sendMessage("我是小娃");
        
    }
}

参考资料：

Java-设计模式(中介模式实现聊天室)_使用设计模式实现聊天室要求真实实现-CSDN博客