java 觀察者模式

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/** 抽象的觀察者 */public interface Watcher {    // status 為 被被觀察著傳遞過來的狀態    public void update(String status);}

import java.util.LinkedList;/** 抽象的被觀察者 */public abstract class Watched {    /** 用來儲存註冊的觀察者對象 */    protected LinkedList<Watcher> watcherList = new LinkedList<Watcher>();    /** 註冊觀察者對象 */    public abstract void add(Watcher watcher);    /** 刪除觀察者對象 */    public abstract void remove(Watcher watcher);    /** 通知所有註冊的觀察者對象 */    public abstract void notifyWatchers();}

// 具體的觀察者public class Boy implements Watcher {    @Override    public void update(String status) {        System.out.println(this + " 監聽到狀態 " + status);    }}

/** 具體的被觀察者: 添加和刪除方法最好加上同步 */public class Girl extends Watched {    private String status;    public void setStatus(String status) {        this.status = status;    }    @Override    public synchronized void add(Watcher watcher) {        watcherList.add(watcher);    }    @Override    public synchronized void remove(Watcher watcher) {        watcherList.remove(watcher);    }    @Override    public void notifyWatchers() {        for (Watcher w : watcherList) {            w.update(status);        }    }}

測試代碼與結果

public class Test {    public static void main(String[] args) throws Exception {        Girl girl = new Girl();        for (int i = 0; i < 3; i++) {            girl.add(new Boy());        }        girl.setStatus("happy");        girl.notifyWatchers();        TimeUnit.SECONDS.sleep(1);        girl.setStatus("unhappy");        girl.notifyWatchers();    }}

 

參考:　

http://www.cnblogs.com/mengdd/archive/2013/02/07/2908929.html

http://www.cnblogs.com/mengdd/archive/2013/02/07/2908929.html

java 觀察者模式