大话设计模式-观察者模式

　　基本简介：观察者<Observer>模式（有时又被称为发布-订阅<Publish/Subscribe>模式、模型-视图<Model/View>模式、源-收听者<Source/Listener>模式或从属者<Dependents>模式）是软件设计模式的一种。在此种模式中，一个目标物件管理所有相依于它的观察者物件，并且在它本身的状态改变时主动发出通知。这通常透过呼叫各观察者所提供的方法来实现。此种模式通常被用来实作事件处理系统。

　　Demo为老板回来了，前台秘书通知办公室里面看NBA、买股票的各个同事。

　　代码：ObserverMain.java-入口类,Subject.java、ScretarySubject.java-发布者类,Observer.java-观察者抽象类,NBAObserver.java、StockObserver.java-具体观察者类。源码

ObserverMain.java-入口类

View Code

 1 package publishSubscribe;

 2 

 3 /**

 4  * 观察者模式

 5  */

 6 public class ObserverMain{

 7     public static void main(String[] args){

 8         ScretarySubject scretary = new ScretarySubject();

 9         scretary.setSubjectState("the boss is come back,work hardly!");

10         NBAObserver nbaObserver = new NBAObserver("NBAObserver", scretary);

11         StockObserver stockObserver = new StockObserver("StockObserver", scretary);

12 

13         scretary.attach(nbaObserver);

14         scretary.attach(stockObserver);

15         scretary.notifyObservers();

16     }

17 

18 }

Subject.java、ScretarySubject.java-发布者类

View Code

 1 package publishSubscribe;

 2 

 3 import java.util.ArrayList;

 4 import java.util.List;

 5 

 6 /**

 7  * 发布者

 8  */

 9 public class Subject {

10 

11   private List<Observer> observerList = new ArrayList<Observer>();

12 

13   public void attach(Observer ob) {

14     this.observerList.add(ob);

15   }

16 

17   public void detach(Observer ob) {

18     this.observerList.remove(ob);

19   }

20   

21   public void notifyObservers(){

22     for(Observer o : observerList){

23       o.update();

24     }

25   }

26 }

View Code

 1 package publishSubscribe;

 2 

 3 public class ScretarySubject extends Subject {

 4   private String subjectState;

 5 

 6   public String getSubjectState() {

 7     return subjectState;

 8   }

 9 

10   public void setSubjectState(String subjectState) {

11     this.subjectState = subjectState;

12   }

13 

14 }

Observer.java-观察者抽象类

View Code

1 package publishSubscribe;

2 

3 /**

4  * 观察者

5  */

6 public abstract class Observer{

7     public abstract void update();

8 }

NBAObserver.java、StockObserver.java-具体观察者类

View Code

 1 package publishSubscribe;

 2 

 3 public class NBAObserver extends Observer {

 4   private String name;

 5   private ScretarySubject sub;

 6 

 7   public NBAObserver(String name, ScretarySubject sub) {

 8     this.name = name;

 9     this.sub = sub;

10   }

11 

12   public String getName() {

13     return name;

14   }

15 

16   public void setName(String name) {

17     this.name = name;

18   }

19   

20   public ScretarySubject getSub() {

21     return sub;

22   }

23 

24   public void setSub(ScretarySubject sub) {

25     this.sub = sub;

26   }

27 

28   @Override

29   public void update() {

30     System.out.println( this.name + "：" + sub.getSubjectState());

31   }

32 

33 }

View Code

 1 package publishSubscribe;

 2 

 3 public class StockObserver extends Observer {

 4   private String name;

 5   private ScretarySubject sub;

 6 

 7   public StockObserver(String name, ScretarySubject sub) {

 8     this.name = name;

 9     this.sub = sub;

10   }

11 

12   public String getName() {

13     return name;

14   }

15 

16   public void setName(String name) {

17     this.name = name;

18   }

19   

20   public ScretarySubject getSub() {

21     return sub;

22   }

23 

24   public void setSub(ScretarySubject sub) {

25     this.sub = sub;

26   }

27 

28   @Override

29   public void update() {

30       System.out.println( this.name + "：" + sub.getSubjectState());

31   }

32 

33 }