Java JDK自带的观察者设计模式

观察者是实现java.util.Observer接口
被观察者是继承java.util.Observable类

package com.cwq.beyond;
import java.util.Observable;
import java.util.Observer;



public class Temo {
	public static void main(String[] args) {
		PersonAll perAPerson = new PersonAll();
		PersonAll perBPerson = new PersonAll();
		PersonAll perCPerson = new PersonAll();
		House house = new House(8000.00);
		house.addObserver(perAPerson);
		house.addObserver(perBPerson);
		house.addObserver(perCPerson);
		house.setPrice(900000);
	}	
}
class PersonAll implements Observer{

	@Override
	public void update(Observable o, Object arg) {
		if (o instanceof House) {
			if (arg instanceof Double) {
				System.out.println("[人民关注]，房价上涨："+ arg);
			}
		}
	}
	
}

class House extends Observable{ // 被观察者
	private double price; // 被观察者
	public House(Double price) {
		this.price = price;
	}
	
	public void setPrice(double price) {
		if (this.price < price) {
			super.setChanged();
			super.notifyObservers(price);
		}
		this.price = price;
	}
	
}