1 /*
2 * Copyright 2000-2006 Sun Microsystems, Inc. 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. Sun designates this
8 * particular file as subject to the "Classpath" exception as provided
9 * 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 /**
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. </p>
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 }
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