【java设计模式】观察者模式

步骤一：建立观察者接口

public interface Observer {
   public void update();
}

步骤二：建立具体观察者

public class Observer1 implements Observer {

	@Override
	public void update() {
		System.out.println("Observer1更新了");
	}

}

public class Observer2 implements Observer {

	@Override
	public void update() {
		System.out.println("Observer2更新了");
	}

}

步骤三：建立抽象被观察者角色 

public interface Subject {
   public void add(Observer observer);
   public void delete(Observer observer);
   public void notifyObserver();
   public void operator();
}

public abstract class AbstractSubject implements Subject {
    private Vector<Observer> vector=new Vector<Observer>();
    
    @Override
    public void add(Observer observer) {
    	vector.add(observer);
    }
    
    @Override
    public void delete(Observer observer) {
    	vector.remove(observer);
    }
    
    @Override
    public void notifyObserver() {
       Enumeration<Observer> enumo=vector.elements();
       while(enumo.hasMoreElements()) {
    	   enumo.nextElement().update();
       }
    }
}

步骤四：建立具体实现的被观察者

public class MySubject extends AbstractSubject{

	@Override
	public void operator() {
		System.out.println("update self");
		notifyObserver();
	}

}

步骤五：测试

public class Test {
    public static void main(String[] args) {
		Subject sub=new MySubject();
		sub.add(new Observer1());
		sub.add(new Observer2());
		sub.operator();
	}
}