[實驗任務一]：股票提醒
當股票的價格上漲或下降5%時，會通知持有該股票的股民，當股民聽到價格上漲的訊息時會買股票，當價格下降時會大哭一場。
實驗要求：
1. 畫出對應類圖；
2. 提交原始碼；
package observer;
import java.util.ArrayList;
public abstract class Subject {
protected ArrayList<MyObserver> observers = new ArrayList<>();
//註冊
public void attach(MyObserver obs){
observers.add(obs);
}
//登出
public void detach(MyObserver obs){
observers.remove(obs);
}
//抽象改變
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，具體目標類
public class Stock extends Subject{
@Override
public void up(double a) {
System.out.println("股票上漲"+(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("股票上漲，買了一些股票");
}
@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. 注意程式設計規範。