01 /*
02 * Copyright 2000-2006 Sun Microsystems, Inc. All Rights Reserved.
03 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
04 *
05 * This code is free software; you can redistribute it and/or modify it
06 * under the terms of the GNU General Public License version 2 only, as
07 * published by the Free Software Foundation. Sun designates this
08 * particular file as subject to the "Classpath" exception as provided
09 * by Sun 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 Sun Microsystems, Inc., 4150 Network Circle, Santa Clara,
22 * CA 95054 USA or visit www.sun.com if you need additional information or
23 * have any questions.
24 */
25
26 package java.nio.channels.spi;
27
28 import java.nio.channels.*;
29
30 /**
31 * Base implementation class for selection keys.
32 *
33 * <p> This class tracks the validity of the key and implements cancellation.
34 *
35 * @author Mark Reinhold
36 * @author JSR-51 Expert Group
37 * @version 1.19, 07/05/05
38 * @since 1.4
39 */
40
41 public abstract class AbstractSelectionKey extends SelectionKey {
42
43 /**
44 * Initializes a new instance of this class. </p>
45 */
46 protected AbstractSelectionKey() {
47 }
48
49 private volatile boolean valid = true;
50
51 public final boolean isValid() {
52 return valid;
53 }
54
55 void invalidate() { // package-private
56 valid = false;
57 }
58
59 /**
60 * Cancels this key.
61 *
62 * <p> If this key has not yet been cancelled then it is added to its
63 * selector's cancelled-key set while synchronized on that set. </p>
64 */
65 public final void cancel() {
66 // Synchronizing "this" to prevent this key from getting canceled
67 // multiple times by different threads, which might cause race
68 // condition between selector's select() and channel's close().
69 synchronized (this ) {
70 if (valid) {
71 valid = false;
72 ((AbstractSelector) selector()).cancel(this);
73 }
74 }
75 }
76 }
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