001    /* Observer.java -- an object that will be informed of changes in an Observable
002       Copyright (C) 1998, 1999, 2001, 2002, 2005  Free Software Foundation, Inc.
003    
004    This file is part of GNU Classpath.
005    
006    GNU Classpath is free software; you can redistribute it and/or modify
007    it under the terms of the GNU General Public License as published by
008    the Free Software Foundation; either version 2, or (at your option)
009    any later version.
010    
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014    General Public License for more details.
015    
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019    02110-1301 USA.
020    
021    Linking this library statically or dynamically with other modules is
022    making a combined work based on this library.  Thus, the terms and
023    conditions of the GNU General Public License cover the whole
024    combination.
025    
026    As a special exception, the copyright holders of this library give you
027    permission to link this library with independent modules to produce an
028    executable, regardless of the license terms of these independent
029    modules, and to copy and distribute the resulting executable under
030    terms of your choice, provided that you also meet, for each linked
031    independent module, the terms and conditions of the license of that
032    module.  An independent module is a module which is not derived from
033    or based on this library.  If you modify this library, you may extend
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035    obligated to do so.  If you do not wish to do so, delete this
036    exception statement from your version. */
037    
038    
039    package java.util;
040    
041    /**
042     * Interface that is implemented when a class wants to be informed of changes
043     * in Observable objects.
044     *
045     * @author Warren Levy (warrenl@cygnus.com)
046     * @see Observable
047     * @status updated to 1.4
048     */
049    public interface Observer
050    {
051      /**
052       * This method is called whenever the observable object changes, and has
053       * called <code>notifyObservers</code>. The Observable object can pass
054       * arbitrary information in the second parameter.
055       *
056       * @param observable the Observable object that changed
057       * @param arg arbitrary information, usually relating to the change
058       */
059      void update(Observable observable, Object arg);
060    }