[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；
package test21;
// 观察者接口，股民
interface Observer {
void update(double price);
}
package test21;
// 具体观察者，股民
class StockInvestor implements Observer {
private String name;
public StockInvestor(String name) {
this.name = name;
}
@Override
public void update(double price) {
if (price > 0) {
System.out.println(name + "收到消息：股票价格上涨，赶紧买入！");
} else {
System.out.println(name + "收到消息：股票价格下跌，大哭一场！");
}
}
}
package test21;
// 主题接口，被观察的对象
interface Subject {
void addObserver(Observer observer);
void removeObserver(Observer observer);
void notifyObservers(double price);
}
package test21;
import java.util.ArrayList;
import java.util.List;
// 具体主题，股票价格
class StockPrice implements Subject {
private double currentPrice;
private List<Observer> observers = new ArrayList<>();
@Override
public void addObserver(Observer observer) {
observers.add(observer);
}
@Override
public void removeObserver(Observer observer) {
observers.remove(observer);
}
@Override
public void notifyObservers(double price) {
for (Observer observer : observers) {
observer.update(price);
}
}
public void setPrice(double newPrice) {
if ((newPrice - currentPrice)>= 0.05 * currentPrice) {
currentPrice = newPrice;
notifyObservers(currentPrice);
}else {
notifyObservers(-1);
}
}
}
package test21;
// 测试
public class Main {
public static void main(String[] args) {
StockPrice stockPrice = new StockPrice();
StockInvestor investor1 = new StockInvestor("王某");
StockInvestor investor2 = new StockInvestor("李某");
stockPrice.addObserver(investor1);
stockPrice.addObserver(investor2);
// 模拟股票价格变化
stockPrice.setPrice(100.0);
stockPrice.setPrice(1.0);
stockPrice.setPrice(110.0);
}
}
2. 提交类图；
3. 注意编程规范。