11.22实验 21：观察者模式

[实验任务一]：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。

实验要求：

1. 画出对应类图；

 

 

2. 提交源代码；

package observer;

 

import java.util.ArrayList;

 

public abstract class Subject {

    protected ArrayList<MyObserver> observers = new ArrayList<>();

 

    //注册

    public void attach(MyObserver obs){

        observers.add(obs);

    }

    //注销

    public void detach(MyObserver obs){

        observers.remove(obs);

    }

    //抽象改变

    public abstract void up(double a);

 

    public abstract void down(double a);

}

package observer;

 

public interface MyObserver {

    void responseUp();

    void responseDown();

}

package observer;

//股票，具体目标类

public class Stock extends Subject{

    @Override

    public void up(double a) {

        System.out.println("股票上涨"+(a*100)+"%");

        if(a>0.05){

            for (MyObserver observer : observers) {

                observer.responseUp();

            }

        }

    }

 

    @Override

    public void down(double a) {

        System.out.println("股票下跌"+(a*100)+"%");

        if(a>0){

            for (MyObserver observer : observers) {

                observer.responseDown();

            }

        }

    }

}

package observer;

 

public class StockHolder implements MyObserver{

    @Override

    public void responseUp() {

        System.out.println("股票上涨，买了一些股票");

    }

 

    @Override

    public void responseDown() {

        System.out.println("股票下跌，哭了");

    }

}

package observer;

 

public class Client {

    public static void main(String[] args) {

        Subject s = new Stock();

        StockHolder h1 = new StockHolder();

        s.attach(h1);

        s.up(0.06);

        System.out.println("-------------------");

        s.down(0.06);

    }

}

 

3. 注意编程规范。