Subject.java class
package ObserverPatt2; import java.util.Collection; public abstract class Subject { Collection observers; abstract void registerObserver(Observer obs); abstract void unregisterObserver(Observer obs); abstract void notifyObservers(); }
Observer.java class
package ObserverPatt2; public abstract class Observer { public abstract void update(); }
PostOffice.java class
public class PostOffice extends Subject { private String address; public PostOffice(String address) { observers = new ArrayList(); this.address = address; } public String getAddress() { return address; } public void setAddress(String address) { this.address = address; } @Override void registerObserver(Observer obs) { observers.add(obs); } @Override void unregisterObserver(Observer obs) { observers.remove(obs); } @Override void notifyObservers() { Iterator iterator = observers.iterator(); while(iterator.hasNext()){ ((ObserverPatt2.MailBox)iterator.next()).update(); } } }
MailBox.java class
package ObserverPatt2; public class MailBox extends Observer { String Id; public MailBox(String id) { Id = id; } public String getId() { return Id; } public void setId(String id) { Id = id; } @Override public void update() { System.out.println(Id + "- Tiene Nuevo email"); } }
MainClass.java
package ObserverPatt2; public class MainClass { public static void main(String... args){ MailBox mailBox1 = new MailBox("Paseo de la Reforma 123"); MailBox mailBox2 = new MailBox("Insurgentes Sur 123"); PostOffice postOffice = new PostOffice("Central de Correos"); System.out.println("registrando observador " + mailBox1.getId() + " en " + postOffice.getAddress() ); postOffice.registerObserver( mailBox1); System.out.println( postOffice.getAddress() + ": notificando a observadores..."); postOffice.notifyObservers(); System.out.println("registrando observador " + mailBox2.getId() + " en " + postOffice.getAddress() ); postOffice.registerObserver( mailBox2); System.out.println( postOffice.getAddress() + ": notificando a observadores..."); postOffice.notifyObservers(); System.out.println("Desregistrando observador " + mailBox1.getId() + " de " + postOffice.getAddress() ); postOffice.unregisterObserver( mailBox1); System.out.println( postOffice.getAddress() + ": notificando a observadores..."); postOffice.notifyObservers(); } }
La corrida quedaría de la siguiente manera:
registrando observador Paseo de la Reforma 123 en Central de Correos
Central de Correos: notificando a observadores...
Paseo de la Reforma 123- Tiene Nuevo email
registrando observador Insurgentes Sur 123 en Central de Correos
Central de Correos: notificando a observadores...
Paseo de la Reforma 123- Tiene Nuevo email
Insurgentes Sur 123- Tiene Nuevo email
Desregistrando observador Paseo de la Reforma 123 de Central de Correos
Central de Correos: notificando a observadores...
Insurgentes Sur 123- Tiene Nuevo email
fin texto.
