1 /*

     2  * Copyright (c) 2000, 2013, Oracle and/or its affiliates. All rights reserved.

     3  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.

     4  *

     5  * This code is free software; you can redistribute it and/or modify it

     6  * under the terms of the GNU General Public License version 2 only, as

     7  * published by the Free Software Foundation.  Oracle designates this

     8  * particular file as subject to the "Classpath" exception as provided

     9  * by Oracle in the LICENSE file that accompanied this code.

    10  *

    11  * This code is distributed in the hope that it will be useful, but WITHOUT

    12  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or

    13  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License

    14  * version 2 for more details (a copy is included in the LICENSE file that

    15  * accompanied this code).

    16  *

    17  * You should have received a copy of the GNU General Public License version

    18  * 2 along with this work; if not, write to the Free Software Foundation,

    19  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.

    20  *

    21  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA

    22  * or visit www.oracle.com if you need additional information or have any

    23  * questions.

    24  */

    25 

    26 package java.nio.channels.spi;

    27 

    28 import java.nio.channels.*;

    29 

    30 

    31 /**

    32  * Base implementation class for selection keys.

    33  *

    34  * <p> This class tracks the validity of the key and implements cancellation.

    35  *

    36  * @author Mark Reinhold

    37  * @author JSR-51 Expert Group

    38  * @since 1.4

    39  */

    40 

    41 public abstract class AbstractSelectionKey

    42     extends SelectionKey

    43 {

    44 

    45     /**

    46      * Initializes a new instance of this class.

    47      */

    48     protected AbstractSelectionKey() { }

    49 

    50     private volatile boolean valid = true;

    51 

    52     public final boolean isValid() {

    53         return valid;

    54     }

    55 

    56     void invalidate() {                                 // package-private

    57         valid = false;

    58     }

    59 

    60     /**

    61      * Cancels this key.

    62      *

    63      * <p> If this key has not yet been cancelled then it is added to its

    64      * selector's cancelled-key set while synchronized on that set.  </p>

    65      */

    66     public final void cancel() {

    67         // Synchronizing "this" to prevent this key from getting canceled

    68         // multiple times by different threads, which might cause race

    69         // condition between selector's select() and channel's close().

    70         synchronized (this) {

    71             if (valid) {

    72                 valid = false;

    73                 ((AbstractSelector)selector()).cancel(this);

    74             }

    75         }

    76     }

    77 }