communicationeventobservable.java

自己写的一个聊天的小程序 请多多指教

/*
 * Copyright (c) 2003 - 2007, Silvio Meier and Tobias Reinhard
 *
 * All rights reserved.
 * 
 * Redistribution and use in source and binary forms, 
 * with or without modification, are permitted provided 
 * that the following conditions are met:
 *
 *   o Redistributions of source code must retain the above 
 *     copyright notice, this list of conditions and the 
 *     following disclaimer.
 *   o Redistributions in binary form must reproduce the above 
 *     copyright notice, this list of conditions and the 
 *     following disclaimer in the documentation and/or other 
 *     materials provided with the distribution.
 *   o The names of its contributors may not be used to endorse 
 *     or promote products derived from this software without 
 *     specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
 * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR
 * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
 * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
 * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
 * PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
 * LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
 * NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
 * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */
package net.sf.cscc;

import java.util.Enumeration;
import java.util.Vector;

/**
 *  This class provides the functionality for observing the communication
 *  events.
 *
 *	@author             Silvio Meier (SM)
 *	@copyright          Silvio Meier, Tobias Reinhard, 2003
 *	@history            2003-05-14 SM First Version
 *                      2003-05-14 SM working on additional methods and events,
 *                      correction of some comments.
 *                      2003-05-20 TR Comments corrected
 *	@version            $Date: 2007/07/01 17:04:05 $, $Author: reode_orm $, $Revision: 1.1 $
 */
class CommunicationEventObservable {

    /**
     * Holds all registerd observers.
     * @directed
     * @label notifies
     */
    private Vector observers;

    /**
     *   This constructor initializes the observable object.
     *
     *   @pre true
     *   @post observers != null
     */
    public CommunicationEventObservable() {
        observers = new Vector();
    }

    /**
     *   Removes a given observer from the list of communication event observers. If the given
     *   observer is not contained in the observer list, nothing happens.
     *   @pre o != null
     *   @post ((observers.size())@pre == (observers.size())@post + 1 &&
     *          (obervers.contains(o))@pre) || (!(observers.contains(o))
     *   @param o Observer which should be eliminated from the observer list.
     */
    public synchronized  void removeCommunicationEventObserver(CommunicationEventObserver o) {
        observers.remove(o);
    }


    /**
     *   Notifies all observers in the observer list by sending them the event.
     *   The observers have to implement the
     *   {@link net.sf.cscc.CommunicationEventObserver}
     *   interface.
     *
     *   @pre ce != null
     *   @post true
     *   @param ce CommunicationEvent object which is sent to the observers.
     */
    public synchronized  void notifyCommunicationEventObservers(CommunicationEvent ce) {
        Enumeration e = observers.elements();
        while (e.hasMoreElements()) {
            Object o = e.nextElement();
            ((CommunicationEventObserver)o).receiveEvent(ce);
        }
    }

    /**
     *   Adds an observer to the communication observer list. If the observer is already
     *   in the list, it is added again, so that multiple event notifications
     *   can happen. The observer may not be null!
     *   @pre  o != null
     *   @post ((observers.size())@pre == (observers.size())@post - 1
     *   @param o Observer to add to the list
     */
    public synchronized void addCommunicationEventObserver(CommunicationEventObserver o) {
        observers.add(o);
    }
}