package apusic.myshop.control.web;import java.util.HashMap;import java.util.ArrayList;import java.util.Collection;import java.util.Iterator;import apusic.myshop.util.Debug;/** * This class is responsible for providing methods to add objects as listeners * for a particular model update event and for notifying the listeners when the * event actually occurs. */ //觀察者模式中的抽象主題public class ModelUpdateNotifier {    private HashMap listenerMap;        //構(gòu)造函數(shù)初始哈西表    public ModelUpdateNotifier() {	    listenerMap = new HashMap();    }        //通知觀察者    public void notifyListeners(Collection updatedModelList) {      for (Iterator it1 = updatedModelList.iterator() ; it1.hasNext() ;) {	      String modelType = (String) it1.next();	      Collection listeners = (Collection)listenerMap.get(modelType);        if (listeners != null) {          for (Iterator it2 = listeners.iterator(); it2.hasNext(); ) {		        ((ModelUpdateListener) it2.next()).performUpdate();	        }        }      }    }    //增加觀察者    public void addListener(String modelType, Object listener) {	    Debug.println("adding " + listener.toString() + "To" + modelType);	    if (listenerMap.get(modelType) == null) {	      ArrayList listeners = new ArrayList();	      listeners.add(listener);	      listenerMap.put(modelType,listeners);	    } else {	      ((ArrayList) listenerMap.get(modelType)).add(listener);	    }    }}