package tutor21;
import java.util.ArrayList;
public class Client {
public static void main(String args[]) {
MySubject subject = new Stock();
MyObserver obs1;
obs1=new Holders();
subject.attach(obs1);
System.out.println("股票上涨");
subject.change(5);
System.out.println("股票下跌");
subject.change(-5);
}
}
class Holders implements MyObserver {
public void response(int rate) {
if(rate>=5) {
System.out.println("股票上涨，买股票");
}else if(rate<=-5){
System.out.println("股票下跌，大哭一场");
}
}
}
interface MyObserver {
void response(int rate);
}
abstract class MySubject {
protected ArrayList<MyObserver> observers = new ArrayList<MyObserver>();
//注册方法
public void attach(MyObserver observer) {
observers.add(observer);
}
//注销方法
public void detach(MyObserver observer) {
observers.remove(observer);
}
//抽象通知方法
public abstract void change(int rate);
}
class Stock extends MySubject {
public void change(int rate) {
for(Object obs : observers) {
((MyObserver)obs).response(rate);
}
}
}
