mediator-pattern.java

public interface Mediator {
    public void send(String message, Colleague colleague);
}

public abstract class Colleague{
    private Mediator mediator;
    public Colleague(Mediator m) {
        mediator = m;
    }
    //send a message via the mediator
    public void send(String message) {
        mediator.send(message, this);
    }
    //get access to the mediator
    public Mediator getMediator() {return mediator;}
    public abstract void receive(String message);
}

public class ApplicationMediator implements Mediator {
    private ArrayList<Colleague> colleagues;
    public ApplicationMediator() {
        colleagues = new ArrayList<Colleague>();
    }
    public void addColleague(Colleague colleague) {
        colleagues.add(colleague);
    }
    public void send(String message, Colleague originator) {
        //let all other screens know that this screen has changed
        for(Colleague colleague: colleagues) {
        //don't tell ourselves
            if(colleague != originator) {
                colleage.receive(message);
            }
        }
    }
}

public class ConcreteColleague extends Colleague {
    public void receive(String message) {
        System.out.println("Colleague Received: " + message);
    }
}

public class MobileColleague extends Colleague {
    public void receive(String message) {
        System.out.println("MobileColleague Received: " + message);
    }
}

public class Client {
    public static void main(String[] args) {
        ApplicationMediator mediator = new ApplicationMediator();
        ConcreteColleague desktopColleague = new ConcreteColleague(mediator);
        ConcreteColleague mobileColleague = new MobileColleague(mediator);
        mediator.addColleague(desktopColleague);
        mediator.addColleague(mobileColleague);
        desktopColleague.send("Hey PC gamers!");
        mobileColleague.send("Hey Mobile gamers!");
    }
}