实验 21：观察者模式
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. 提交源代码；
C++
#include<iostream>
#include<list>
using namespace std;
class MyObserver {
public:
virtual void response(int rate) {};
};
class MySubject {
protected:
list<MyObserver*>observers;
public:
/*注册方法*/
void attach(MyObserver*observer) {
observers.push_back(observer);
};
/*注销方法*/
void detach(MyObserver* observer) {
observers.remove(observer);
}
/*抽象通知方法*/
virtual void change(int rate) = 0;
};
class Stock : public MySubject {
public:
void change(int rate) {
list<MyObserver*>::iterator iter = observers.begin();
for (; iter != observers.end(); iter++)
(*iter)->response(rate);
}
};
class Holders :public MyObserver {
public:
void response(int rate) {
if (rate >= 5) {
cout << "股票上涨，购买股票" << endl;
}
else if (rate <= -5) {
cout << "股票下跌，大哭一场" << endl;
}
else {
cout << "股票还比较稳定哦~" << endl;
}
}
};
int main() {
MySubject* subject = new Stock();
MyObserver*obs1 = new Holders();
subject->attach(obs1);
cout << "----------------------股票上涨-----------------------" << endl;
subject->change(5);
cout << endl;
cout << "----------------------股票下跌-----------------------" << endl;
subject->change(-5);
cout << endl;
cout << "----------------------股票稳定-----------------------" << endl;
subject->change(4);
cout << endl;
}
运行结果：
Java
package observer_pattern;
public interface Guancha {
public void sheng();
public void jiang();
}
package observer_pattern;
public class Gumin implements Guancha{
private String name;
public Gumin(String a){name=a;}
public void sheng(){
System.out.println(name+"买了一些股票（股票升了）");
}
public void jiang(){
System.out.println("股票降价了，哭了");
}
}
package observer_pattern;
import java.util.ArrayList;
public class Fen{
private ArrayList<Guancha> oblist;
public Fen(){
oblist=new ArrayList<>();
}
public void add(Guancha a){
oblist.add(a);
}
public void remove(Guancha a){
oblist.remove(a);
}
public void sheng(double a){
if(a>0.05)
for(Guancha guan:oblist){
guan.sheng();
}
}
public void jiang(double a){
if(a>0.05)
for(Guancha guan:oblist){
guan.jiang();
}
}
}
package observer_pattern;
public class main {
public static void main(String[] args) {
Fen f=new Fen();
Gumin g1=new Gumin("第一个股民");
Gumin g2=new Gumin("第二个股民");
f.add(g1);
f.add(g2);
System.out.println("股票升了");
f.sheng(0.1);
System.out.println("比率小于0.05");
System.out.println();
f.sheng(0.001);
System.out.println("股票降了");
f.jiang(0.1);
System.out.println("比率小于0.05");
System.out.println();
f.jiang(0.001);
}
}
运行结果：
2. 提交类图；
