java 觀察者模式

IWatched：

/** * @author com.tiantian * @version 建立時間：2012-11-20 下午4:58:25 */public interface IWatched {    public void addWatcher(IWatcher watcher);    public void removeWatcher(IWatcher watcher);    public void notifyWatchers(String msg);}

IWatcher：

/** * @author com.tiantian * @version 建立時間：2012-11-20 下午4:55:23 */public interface IWatcher {    public void update(String msg);}

Watched：

/** * @author com.tiantian * @version 建立時間：2012-11-20 下午5:01:05 */public class Watched implements IWatched{    private List<IWatcher> watchers = new ArrayList<IWatcher>();    @Override    public void addWatcher(IWatcher watcher) {        watchers.add(watcher);    }    @Override    public void removeWatcher(IWatcher watcher) {        watchers.remove(watcher);    }    @Override    public void notifyWatchers(String msg) {        for(IWatcher watcher : watchers){            watcher.update(msg);        }    }}

Watcher：

/** * @author com.tiantian * @version 建立時間：2012-11-20 下午5:04:56 */public class Watcher implements IWatcher{    @Override    public void update(String msg) {        System.out.println(msg);    }}

Test：

/** * @author com.tiantian * @version 建立時間：2012-11-20 下午5:05:26 */public class Test {    public static void main(String[] args) {        IWatched watched = new Watched();        IWatcher watcher1 = new Watcher();        IWatcher watcher2 = new Watcher();        IWatcher watcher3 = new Watcher();        watched.addWatcher(watcher1);        watched.addWatcher(watcher2);        watched.addWatcher(watcher3);        watched.notifyWatchers("I have been clicked!");                watched.removeWatcher(watcher1);        watched.notifyWatchers("what's up");    }}