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；
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();
}
2. 提交类图；
3. 注意编程规范。