package org.jutil.event;import java.util.EventListener;import java.util.EventObject;/** * <p>Instances of this type add the posibility for users to <em>ask</em> *   whether the instance is applicable to a given listener/event *   combination.</p> * <p>The {@link ChainNotifier} chains instances of this type. It uses *   {@link isApplicable(EventListener, EventObject)} to decide whether *   or not to use a particular applicability notifier to notify a *   particular listener with a particular event.</p> * <p>The actual preconditions of the method *   {@link Notifier#notifyEventListener(EventListener, EventObject)} may be *   stronger than this method. {@link isApplicable(EventListener, *   EventObject)} should only test just enough to determine *   whether or not the intance can deal with this listener/event *   combination <em>in the context of the listener/event combinations that *   actually will be offered to it</em>. E.g., if we know for sure that *   the event argument will never be null, this method does not have to *   return <literal>false</literal> if it is called with an actual null argument, *   although the model method {@link Notifier#isValidEvent(EventObject) *   does. More specifically, there does not have to be code to check this. The *   specification is written this way in the interest of performance.</p> * <p>Typically, the method checks the type of the listener. *   {@link TypeApplicabilityNotifier} is a subclass that offers support *   for this.</p> * <pre> * ... * * /oo *   o also *   o   public behavior *   o     pre listener != null; *   o     post \result == listener instanceof <var>EventName</var>Listener; *   oo/ * public boolean isApplicable(EventListener listener, EventObject event) { *   return (listener instanceof <var>EventName</var>Listener); * } * </pre> * * @path    $Source: /cvsroot/org-jutil/jutil.org/src/org/jutil/event/ApplicabilityNotifier.java,v $ * @version $Revision: 1.4 $ * @date    $Date: 2002/09/07 08:55:49 $ * @state   $State: Exp $ * @author  Jan Dockx * @release $Name:  $ */public interface ApplicabilityNotifier extends Notifier {	/* The revision of this class */	public final static String CVS_REVISION ="$Revision: 1.4 $";  /**   * <p>If a listener or event is valid, then this must return true.   *   The implication in the formal specification means that the   *   model methods can be stronger than the implementation of this   *   method. This method only needs to test things which cannot be   *   proven.</p>   */ /*@   @ public behavior   @   pre listener != null;   @   post \result <== isValidListener(listener) && isValidEvent(event);   @*/  public boolean isApplicable(EventListener listener, EventObject event);        }/* * <copyright>Copyright (C) 1997-2002. This software is copyrighted by  * the people and entities mentioned after the "@author" tags above, on  * behalf of the JUTIL.ORG Project. The copyright is dated by the dates  * after the "@date" tags above. All rights reserved. * This software is published under the terms of the JUTIL.ORG Software * License version 1.1 or later, a copy of which has been included with * this distribution in the LICENSE file, which can also be found at * http://org-jutil.sourceforge.net/LICENSE. This software is distributed  * WITHOUT ANY WARRANTY; without even the implied warranty of  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  * See the JUTIL.ORG Software License for more details. For more information, * please see http://org-jutil.sourceforge.net/</copyright> */