STOCK
import java.util.*;
//抽象股民：抽象观察者
interface Investor
{public void response(Stock stock);
}
//股票：观察目标
class Stock
{ private ArrayList<Investor> investors;
private String stockName;
private double price;
public Stock(String stockName,double price){
this.stockName = stockName;
this.price = price;
investors = new ArrayList<Investor>();
}
public void attach(Investor investor)
{investors.add(investor);
}
public void detach(Investor investor)
{investors.remove(investor);
}
public void setStockName(String stockName)
{this.stockName = stockName;
}
public String getStockName()
{return this.stockName;
}
public void setPrice(double price)
{double range = Math.abs(price-this.price)/this.price;
this.price = price;
if(range>=0.05)
{this.notifyInvestor();
}
}
public double getPrice()
{return this.price;
}
public void notifyInvestor()
{for(Object obj:investors)
{((Investor)obj).response(this);
}
}
}
//股民：具体观察者
class ConcreteInvestor implements Investor
{
private String name;
public ConcreteInvestor(String name)
{
this.name = name;
}
public void response(Stock stock)
{
System.out.print("提示股民: " + name);
System.out.print("------股票：" + stock.getStockName());
System.out.print("价格波动幅度超过5%------") ;
System.out.println("新价格是:"+ stock.getPrice() + "。");
}
}
//客户端测试类
class Client
{
public static void main(String args[])
{
Investor investor1,investor2;
investor1 = new ConcreteInvestor("yuquanA");
investor2 = new ConcreteInvestor("yuquanB");
Stock haier = new Stock("东风汽车",20.00);
haier.attach(investor1); //注册
haier.attach(investor2); //注册
haier.setPrice(25.00);
}
}
