1 import java.util.ArrayList;
 2 import java.util.List;
 3 
 4 public class Main
 5 {
 6     public static void main(String[] args)
 7     {
 8         Subject sub = new ConcreteSubject();
 9         sub.addObserver(new ConcreteObserver1()); //添加观察者1
10         sub.addObserver(new ConcreteObserver2()); //添加观察者2
11         sub.doSomething();
12     }
13 
14     /**
15      * 观察则接口
16      */
17     public interface Observer
18     {
19         void update();
20     }
21 
22     /**
23      * 被观察者基类
24      */
25     public static abstract class Subject
26     {
27         private List<Observer> obs = new ArrayList<>();
28 
29         public void addObserver(Observer obs)
30         {
31             this.obs.add(obs);
32         }
33 
34         public void delObserver(Observer obs)
35         {
36             this.obs.remove(obs);
37         }
38 
39         protected void notifyObserver()
40         {
41             for (Observer o : obs)
42             {
43                 o.update();
44             }
45         }
46 
47         public abstract void doSomething();
48     }
49 
50     /**
51      * 观察者对象1
52      */
53     public static class ConcreteObserver1 implements Observer
54     {
55         public void update()
56         {
57             System.out.println("观察者1收到信息，并进行处理。");
58         }
59     }
60 
61     /**
62      * 观察者对象2
63      */
64     public static class ConcreteObserver2 implements Observer
65     {
66         public void update()
67         {
68             System.out.println("观察者2收到信息，并进行处理。");
69         }
70     }
71 
72     /**
73      * 具体的被观察者
74      */
75     public static class ConcreteSubject extends Subject
76     {
77         public void doSomething()
78         {
79             System.out.println("被观察者事件反生");
80             this.notifyObserver();
81         }
82     }
83 }