觀察者模式
//抽象主題
package com.shengsiyuan.observer;
//抽象主題，被觀察者的抽象
public interface Watched
{
public void addWatcher(Watcher watcher);
public void removeWatcher(Watcher watcher);
public void notifyWatchers(String str);
}
//具體主題
import java.util.ArrayList;
import java.util.List;
public class ConcreteWatched implements Watched
{
private List<Watcher> list = new ArrayList<Watcher>();
@Override
public void addWatcher(Watcher watcher)
{
list.add(watcher);
}
@Override
public void removeWatcher(Watcher watcher)
{
list.remove(watcher);
}
@Override
public void notifyWatchers(String str)
{
for(Watcher watcher : list)
{
watcher.update(str);
}
}
}
//抽象觀察者
public interface Watcher
{
public void update(String str);
}
//具體觀察者
public class ConcreteWatcher implements Watcher
{
@Override
public void update(String str)
{
System.out.println(str);
}
}
//測試類，測試觀察者模式
public class Test
{
public static void main(String[] args)
{
Watched girl = new ConcreteWatched();
Watcher watcher1 = new ConcreteWatcher();
Watcher watcher2 = new ConcreteWatcher();
Watcher watcher3 = new ConcreteWatcher();
girl.addWatcher(watcher1);
girl.addWatcher(watcher2);
girl.addWatcher(watcher3);
girl.notifyWatchers("開心，爽");
girl.removeWatcher(watcher2);
girl.notifyWatchers("不爽");
}
}
//自個分析：具體主題girl類似於GUI中的組件button，addWatcher()方法類似於addActionListener()方法，wahcher1類似於ActionEvent e中的e對象.另外，其它removeWatcher和notifyWathcers()方法類似於button的其它方法。抽象觀察者類似接口型的事件監聽器，具體觀察者，類似實現類型的適配器。