001    /* AbstractSelectionKey.java --
002       Copyright (C) 2002, 2003, 2004, 2006  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    
011    GNU Classpath is distributed in the hope that it will be useful, but
012    WITHOUT ANY WARRANTY; without even the implied warranty of
013    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
014    General Public License for more details.
015    
016    You should have received a copy of the GNU General Public License
017    along with GNU Classpath; see the file COPYING.  If not, write to the
018    Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
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
034    this exception to your version of the library, but you are not
035    obligated to do so.  If you do not wish to do so, delete this
036    exception statement from your version. */
037    
038    package java.nio.channels.spi;
039    
040    import java.nio.channels.SelectionKey;
041    
042    
043    /**
044     * @since 1.4
045     */
046    public abstract class AbstractSelectionKey extends SelectionKey
047    {
048      private boolean cancelled;
049    
050      /**
051       * Initializes the key.
052       */
053      protected AbstractSelectionKey()
054      {
055      }
056    
057      /**
058       * Cancels this key.
059       */
060      public final synchronized void cancel()
061      {
062        if (isValid())
063          {
064            ((AbstractSelector) selector()).cancelKey(this);
065            cancelled = true;
066          }
067      }
068    
069      /**
070       * Tells whether this key is valid or not.
071       *
072       * @return true if this key is valid, false otherwise
073       */
074      public final synchronized boolean isValid()
075      {
076        return ! cancelled;
077      }
078    }