设计模式之中介者模式（Mediator模式）

• Client:

public class Client {
    public static void main(String[] args) {
        Mediator mediator = new ConcreteMediator();
        Colleague colleague = new ConcreteColleague();
        mediator.register(colleague);
        colleague.send();
    }
}

• Mediator:

public interface Mediator {
    void register(Colleague colleague);

    void relay(Colleague colleague);
}

• ConcreteMediator:

public class ConcreteMediator implements Mediator{
    private List colleagues = new ArrayList<>();

    @Override
    public void register(Colleague colleague) {
        if (!colleagues.contains(colleague)) {
            colleague.setMediator(this);
            colleagues.add(colleague);
        }
    }

    @Override
    public void relay(Colleague colleague) {
        colleague.receive();
    }
}

• Colleague:

public abstract class Colleague {
    protected Mediator mediator = null;

    public void setMediator(Mediator mediator) {
        this.mediator = mediator;
    }

    public abstract void receive();

    public abstract void send();
}

• ConcreteColleague:

public class ConcreteColleague extends Colleague{
    @Override
    public void receive() { }

    @Override
    public void send() {
        mediator.relay(this);
    }
}

• Client（客户端）:
  客户端角色，程序的调用者。
• Mediator（中介者）:
  该角色负责定义与Colleague角色进行通信和做出决定的接口。
• ConcreteMediator（具体的中介者）:
  该角色负责实现Mediator角色的接口，负责实际做出决定。
• Colleague（同事）:
  该角色负责定义与Mediator角色进行通信的接口。
• ConcreteColleague（具体的同事）:
  该角色负责实现Colleague角色的接口。