被观察对象内保存全部观察者信息,被观察对象更新时通知每个观察者对象。
代码如下:
//观察者 接口
public interface Observer {
public void update(Subject subject);
}
//观察者实现类
public class MyObserverA implements Observer{
@Override
public void update(Subject subject) {
System.out.println("a is updated");
}
}
public class MyObserverB implements Observer{
@Override
public void update(Subject subject) {
System.out.println("b is updated");
}
}
//被观察者
public class Subject {
private static Vector obs = new Vector();
//注册观察者
public static void attach(Observer ob){
obs.add(ob);
}
//解除与注册者关联
public static void dettach(Observer ob){
obs.remove(ob);
}
//操作
public void operatio(){
//执行操作
//通知所有观察者
Enumeration elements = obs.elements();
while(elements.hasMoreElements()){
elements.nextElement().update(this);
}
}
}
//测试
public class Client {
public static void main(String[] args) {
Subject.attach(new MyObserverA());
Subject.attach(new MyObserverB());
Subject subject = new Subject();
subject.operatio();
}
}