11.21

实验 21：观察者模式

本次实验属于模仿型实验，通过本次实验学生将掌握以下内容：

1、理解观察者模式的动机，掌握该模式的结构；

2、能够利用观察者模式解决实际问题。

 

[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 test21;

 

import java.util.ArrayList;

public class Gufen extends Subject{

    public void up(){

        System.out.println("****股份上涨15%****");

        for(Observer guan:observers){

            guan.buy();

        }

    }

    public void down(){

        System.out.println("****股份下跌15%****");

        for(Observer guan:observers){

            guan.cry();

        }

    }

}

 

package test21;

 

public class Gumin implements Observer{

    private String name;

    public Gumin(String a){name=a;}

    public void buy(){

        System.out.println("股民"+name+"买了一些股票");

    }

    public void cry(){

        System.out.println("股民"+name+"哭了");

    }

}

 

package test21;

 

public class main {

    public static void main(String[] args) {

        Gufen f=new Gufen();

        Gumin g1=new Gumin("小张");

        Gumin g2=new Gumin("小龚");

        f.attach(g1);

        f.attach(g2);

        f.up();

        f.down();

    }

}

package test21;

 

 

 

public interface Observer {

      public void buy();

      public void cry();

  }

 

package test21;

 

import java.util.ArrayList;

 

public abstract class Subject {

    protected ArrayList<Observer> observers;

    public Subject(){

        observers=new ArrayList<>();

    }

    public void attach(Observer a){

        observers.add(a);

    }

    public void detach(Observer a){

        observers.remove(a);

    }

    public abstract void up();

    public abstract void down();

}

 

#include<iostream>

#include<list>

#include<string>

using namespace std;

//抽象观察者

class Observer{

protected:

    string name;

public:

    virtual void buy()=0;

    virtual void cry()=0;

};

//具体观察者

class Gumin:public Observer{

public:

    Gumin(string name){

        this->name=name;

    }

    void buy(){

        cout<<"股民"<<name<<"买了一些股票"<<endl;

    }

    void cry(){

        cout<<"股民"<<name<<"哭了"<<endl;

    }

};

//抽象主题类

class Subject{

protected:

    list<Observer*> observers;

public:

    void attach(Observer *obs){

        observers.push_back(obs);

    }

    void detach(Observer *obs){

        observers.remove(obs);

    }

    virtual void up()=0;

    virtual void down()=0;

};

//具体主题类

class Gufen:public Subject{

public:

    void up(){

        cout<<"*****股份上涨15%*****"<<endl;

        list<Observer*>::iterator iter = observers.begin();

        for(; iter != observers.end(); iter++)

            (*iter)->buy();

    }

    void down(){

        cout<<"*****股份下跌15%*****"<<endl;

        list<Observer*>::iterator iter = observers.begin();

        for(; iter != observers.end(); iter++)

            (*iter)->cry();

    }

};

//测试函数

int main(){

    Observer *obs1,*obs2;

    obs1=new Gumin("小张");

    obs2=new Gumin("小龚");

    Subject *sub;

    sub=new Gufen();

    sub->attach(obs1);

    sub->attach(obs2);

    sub->up();

    sub->down();

}