Dyuichi Blog

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

// Mediator
interface Mediator {
    void register(Colleague colleague);
    void relay(Colleague colleague);
}

// Concrete Mediator
class ConcreteMediator implements Mediator {
    private List<Colleague> colleagues = new ArrayList<>();
    @Override
    public void register(Colleague colleague) {
        if (!colleagues.contains(colleague)) {
            colleagues.add(colleague);
            colleague.setMediator(this);
        }
    }
    @Override
    public void relay(Colleague colleague) {
        for (Colleague ob : colleagues) {
            if (!ob.equals(colleague)) {
                ((Colleague) ob).receive();
            }
        }
    }
}

// Colleague
abstract class Colleague {
    protected Mediator mediator;
    public void setMediator(Mediator mediator) {
        this.mediator = mediator;
    }
    public abstract void receive();
    public abstract void send();
}

// Concrete Colleague
class ConcreteColleagueA extends Colleague {
    @Override
    public void receive() {
        System.out.println("ConcreteColleagueA receive");
    }
    @Override
    public void send() {
        System.out.println("ConcreteColleagueA send");
        mediator.relay(this);
    }
}

class ConcreteColleagueB extends Colleague {
    @Override
    public void receive() {
        System.out.println("ConcreteColleagueB receive");
    }
    @Override
    public void send() {
        System.out.println("ConcreteColleagueB send");
        mediator.relay(this);
    }
}

// Client
public class MediatorPattern {
    public static void main(String[] args) {
        Mediator mediator = new ConcreteMediator();
        Colleague colleagueA = new ConcreteColleagueA();
        Colleague colleagueB = new ConcreteColleagueB();
        mediator.register(colleagueA);
        mediator.register(colleagueB);
        colleagueA.send();
        colleagueB.send();
    }
}