java 观察者模式设计方法

 1 import java.util.Observable;
 2 import java.util.Observer;
 3 class House extends Observable {
 4     private float price;
 5     public House(float price){
 6         this.price=price;
 7     }
 8     public float getPrice(){
 9         return price;
10     }
11     public void setPrice(float price){
12         super.setChanged();
13         super.notifyObservers(price);
14         this.price=price;
15     }
16     public String toString(){
17         return "房子价格："+this.price;
18     }
19 }
20 class HousePriceObserver implements Observer{
21     private String name;
22     public HousePriceObserver(String name){
23         this.name=name;
24     }
25     public void update(Observable obj,Object arg){
26         if(arg instanceof Float){
27             System.out.print(this.name+"观察者看到的价格:");
28             System.out.println(((Float) arg).floatValue());
29         }
30     }
31 }
32 public class ObserDemo {
33     public static void main(String[] args) {
34         House h=new House(1000000);
35         HousePriceObserver hp1=new HousePriceObserver("A");
36         HousePriceObserver hp2=new HousePriceObserver("B");
37         HousePriceObserver hp3=new HousePriceObserver("C");
38         h.addObserver(hp1);
39         h.addObserver(hp2);
40         h.addObserver(hp3);
41         System.out.println(h);
42         h.setPrice(6666);
43         System.out.println(h);
44     }
45 }