java笔试题-> 观察者设计模式2

import java.util.Vector;

//观察者设计模式

public class ObserverClient

{
public static void main(String[] args) 
{
Subject sub=new Event();
sub.attach(new observer1());
sub.attach(new observer2());
sub.doSomething();
}

}

abstract class Subject

{
Vector<Observer> vector=new Vector<Observer>();

public void attach(Observer o)
{
vector.add(o);
}

public void detach(Observer o)
{
vector.remove(o);
}

public void notifyObserver()
{
for(Observer o : vector)
{
o.update();
}
}

public abstract void doSomething();

}

class Event extends Subject

{
public void doSomething()
{
notifyObserver();
}

}

interface Observer

{
public void update();

}

class observer1 implements Observer

{
public void update() {
System.out.println("observer1 be updated");
}

}

class observer2 implements Observer

{
public void update() {
System.out.println("observer2 be updated");
}

}