设计模式（13）---观察者模式

 1 import java.util.ArrayList;
 2 
 3 /*
 4  * 抽象观察目标类
 5  */
 6 public abstract class Subject {
 7 
 8     //存储所有具体的观察者
 9     protected ArrayList<Observer> players = new ArrayList<Observer>(); 
10     public Subject() {
11         
12     }
13     
14     //加入方法  
15     public void attach(Observer obs) {  
16         System.out.println(obs.getName() + "加入");  
17         players.add(obs);  
18     }  
19       
20     //退出方法  
21     public void detach(Observer obs) {  
22         System.out.println(obs.getName() + "退出");  
23         players.remove(obs);  
24     }  
25     
26     //声明抽象通知方法  
27     public abstract void notify(String name);  
28 
29 }

 1 /*
 2  * 具体观察目标类
 3  */
 4 public class ConcreteSubject extends Subject {
 5 
 6     public ConcreteSubject() {
 7         // TODO Auto-generated constructor stub
 8     }
 9 
10     @Override
11     public void notify(String name) {
12         //遍历观察者集合，调用每一个观察者（自己除外）的更新方法  
13         for(Object obs : players) {  
14             if (!((Observer)obs).getName().equalsIgnoreCase(name)) {  
15                 ((Observer)obs).update();  
16             }  
17         }       
18 
19     }
20 
21 }

 1 /*
 2  * 抽象观察者
 3  */
 4 interface  Observer {
 5 
 6     public String getName();  
 7     public void setName(String name);  
 8     public void update(); 
 9     public void beAttacked(Subject s); 
10 
11 }

 1 /*
 2  * 具体观察者
 3  */
 4 public class ConcreteObserver implements Observer {
 5 
 6     private String name;
 7     public ConcreteObserver(String name) {
 8         this.name = name;  
 9     }
10     @Override
11     public String getName() {
12         return this.name; 
13     }
14     @Override
15     public void setName(String name) {
16         this.name = name; 
17 
18     }
19 
20     //更新自己的状态
21     @Override
22     public void update() {
23         System.out.println(name+"前去支援");
24 
25     }
26 
27     @Override
28     public void beAttacked(Subject s) {
29         System.out.println(name+"遭到攻击");
30         s.notify(this.name);
31 
32     }
33 
34 }

 1 public class Test {
 2 
 3     public static void main(String[] args) {
 4         ConcreteSubject s = new ConcreteSubject() ;
 5         
 6         Observer o1,o2,o3 ;
 7         o1 = new ConcreteObserver("A队员");
 8         o2 = new ConcreteObserver("B队员");
 9         o3 = new ConcreteObserver("C队员");
10         
11         s.attach(o1);
12         s.attach(o2);
13         s.attach(o3);
14         
15         o1.beAttacked(s);
16 
17     }
18 
19 }