观察者模式(java)

观察者模式:股票提醒

当股票的价格上涨或下降5%时,会通知持有该股票的股民,当股民听到价格上涨的消息时会买股票,当价格下降时会大哭一场。

java源代码:

(1)Client.java:

package shiyan21;

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("");

 

System.out.println("****股票下跌****");

subject.change(-5);

System.out.println("");

 

System.out.println("****股票稳定****");

subject.change(4);

System.out.println("");

}

}

(2)Holders.java:

package shiyan21;

public class Holders implements MyObserver {

public void response(int rate) {

if(rate>=5) {

System.out.println("股票上涨,买买买");

}else if(rate<=-5){

System.out.println("股票下跌,大哭一场");

}else {

System.out.println("股票比较稳定,还好还好");

}

}

}

 

(3)MyObserver.java:

package shiyan21;

public interface MyObserver {

void response(int rate);

}

 

(4)MySubject.java:

package shiyan21;

import java.util.ArrayList;

public 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);

}

 

(5)Stock.java:

package shiyan21;

public class Stock extends MySubject {

public void change(int rate) {

for(Object obs : observers) {

((MyObserver)obs).response(rate);

}   

    }

}

  

实现截图:

观察者模式(java)

 

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