/**
*Mediator Interface
*/
package com.journaldev.design.mediator;public interface ChatMediator {public void sendMessage(String msg, User user);void addUser(User user);
}/**
*Colleague Interface
*/
package com.journaldev.design.mediator;public abstract class User {protected ChatMediator mediator;protected String name;public User(ChatMediator med, String name){this.mediator=med;this.name=name;}public abstract void send(String msg);public abstract void receive(String msg);
}/**
*Concrete Mediator
*/
package com.journaldev.design.mediator;import java.util.ArrayList;
import java.util.List;public class ChatMediatorImpl implements ChatMediator {private List<User> users;public ChatMediatorImpl(){this.users=new ArrayList<>();}@Overridepublic void addUser(User user){this.users.add(user);}@Overridepublic void sendMessage(String msg, User user) {for(User u : this.users){//message should not be received by the user sending itif(u != user){u.receive(msg);}}}}/**
*Concrete Colleague
*/
package com.journaldev.design.mediator;public class UserImpl extends User {public UserImpl(ChatMediator med, String name) {super(med, name);}@Overridepublic void send(String msg){System.out.println(this.name+": Sending Message="+msg);mediator.sendMessage(msg, this);}@Overridepublic void receive(String msg) {System.out.println(this.name+": Received Message:"+msg);}}/**
*Mediator Pattern Client
*/
package com.journaldev.design.mediator;public class ChatClient {public static void main(String[] args) {ChatMediator mediator = new ChatMediatorImpl();User user1 = new UserImpl(mediator, "Pankaj");User user2 = new UserImpl(mediator, "Lisa");User user3 = new UserImpl(mediator, "Saurabh");User user4 = new UserImpl(mediator, "David");mediator.addUser(user1);mediator.addUser(user2);mediator.addUser(user3);mediator.addUser(user4);user1.send("Hi All");}}