forecastdisplay.java

基于股票价格变化的观察者模式的java源代码。初学者可看

import java.lang.Math;

public class ForecastDisplay implements Observer,
  DisplayElement{
	private float price;
	float averagePrice;       //股票的平均价格
	private int count = 0;    //价格变动次数
	float  forecast;          //当前价格和平均价格之差,来预测价格趋势
	private Stock stockData;
	public ForecastDisplay(Stock stockData){
		this.stockData = stockData;
		stockData.registerObserver(this);
	}
	public void update(float price){
		count++;
		this.price = price;
		
		averagePrice = (averagePrice*(count-1) + price)
        /count;
		forecast = averagePrice - price; 
		if(forecast < 0)
			forecast = 0f - forecast;
		display();
	}
	public void display(){
		if(forecast <= 1)
			System.out.println("这支股票价格比较稳定,可以考虑购买.");
		else if(forecast > 1 && forecast <= 2)
			System.out.println("这支股票价格一般稳定,可以考虑购买.");
		else if(forecast > 2 && forecast <= 3)
			System.out.println("这支股票价格勉强稳定,可以考虑购买.");
		else if(forecast > 3 && forecast <= 5)
			System.out.println("这支股票价格有些不稳定,谨慎购买!");
		else 
			System.out.println("这支股票价格波动较大,还是别买了!");
	}
}