Define an object that encapsulates how a set of objects interact. Mediator promotes loose coupling by keeping objects from referring to each other explicitly, and it lets you vary their interaction independently.
Participants
- Mediator: defines an interface for communicating with Colleague objects
- ConcreteMediator: implements cooperative behavior by coordinating Colleague objects. Knows and maintains its colleagues
- Colleague classes: each Colleague class knows its Mediator object. Each colleague communicates with its mediator whenever it would have otherwise communicated with another colleague
Code
public class Main {
public static void main(String[] args) {
ConcreteMediator m = new ConcreteMediator();
ConcreteColleague1 c1 = new ConcreteColleague1(m);
ConcreteColleague2 c2 = new ConcreteColleague2(m);
m.setColleague1(c1);
m.setColleague2(c2);
c1.send("From c1");
c2.send("From c2");
}
}
public interface Mediator {
void send(String message, Colleague colleague);
}
public class ConcreteMediator implements Mediator {
private ConcreteColleague1 colleague1;
private ConcreteColleague2 colleague2;
public void setColleague1(ConcreteColleague1 colleague1) {
this.colleague1 = colleague1;
}
public void setColleague2(ConcreteColleague2 colleague2) {
this.colleague2 = colleague2;
}
@Override
public void send(String message, Colleague colleague) {
if (colleague == colleague1) {
colleague2.notify(message);
} else {
colleague1.notify(message);
}
}
}
public abstract class Colleague {
protected Mediator mediator;
public Colleague(Mediator mediator) {
this.mediator = mediator;
}
}
public class ConcreteColleague1 extends Colleague {
public ConcreteColleague1(Mediator mediator) {
super(mediator);
}
public void send(String message) {
mediator.send(message, this);
}
public void notify(String message) {
System.out.println("Colleague1 gets message: " + message);
}
}
public class ConcreteColleague2 extends Colleague {
public ConcreteColleague2(Mediator mediator) {
super(mediator);
}
public void send(String message) {
mediator.send(message, this);
}
public void notify(String message) {
System.out.println("Colleague2 gets message: " + message);
}
}
Output
Colleague2 gets message: From c1
Colleague1 gets message: From c2
Top comments (0)