01 /*
02 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
03 *
04 * This code is free software; you can redistribute it and/or modify it
05 * under the terms of the GNU General Public License version 2 only, as
06 * published by the Free Software Foundation. Sun designates this
07 * particular file as subject to the "Classpath" exception as provided
08 * by Sun in the LICENSE file that accompanied this code.
09 *
10 * This code is distributed in the hope that it will be useful, but WITHOUT
11 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
12 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
13 * version 2 for more details (a copy is included in the LICENSE file that
14 * accompanied this code).
15 *
16 * You should have received a copy of the GNU General Public License version
17 * 2 along with this work; if not, write to the Free Software Foundation,
18 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
19 *
20 * Please contact Sun Microsystems, Inc., 4150 Network Circle, Santa Clara,
21 * CA 95054 USA or visit www.sun.com if you need additional information or
22 * have any questions.
23 */
24
25 /*
26 * This file is available under and governed by the GNU General Public
27 * License version 2 only, as published by the Free Software Foundation.
28 * However, the following notice accompanied the original version of this
29 * file:
30 *
31 * Written by Doug Lea with assistance from members of JCP JSR-166
32 * Expert Group and released to the public domain, as explained at
33 * http://creativecommons.org/licenses/publicdomain
34 */
35
36 package java.util.concurrent.locks;
37
38 /**
39 * A synchronizer that may be exclusively owned by a thread. This
40 * class provides a basis for creating locks and related synchronizers
41 * that may entail a notion of ownership. The
42 * <tt>AbstractOwnableSynchronizer</tt> class itself does not manage or
43 * use this information. However, subclasses and tools may use
44 * appropriately maintained values to help control and monitor access
45 * and provide diagnostics.
46 *
47 * @since 1.6
48 * @author Doug Lea
49 */
50 public abstract class AbstractOwnableSynchronizer implements
51 java.io.Serializable {
52
53 /** Use serial ID even though all fields transient. */
54 private static final long serialVersionUID = 3737899427754241961L;
55
56 /**
57 * Empty constructor for use by subclasses.
58 */
59 protected AbstractOwnableSynchronizer() {
60 }
61
62 /**
63 * The current owner of exclusive mode synchronization.
64 */
65 private transient Thread exclusiveOwnerThread;
66
67 /**
68 * Sets the thread that currently owns exclusive access. A
69 * <tt>null</tt> argument indicates that no thread owns access.
70 * This method does not otherwise impose any synchronization or
71 * <tt>volatile</tt> field accesses.
72 */
73 protected final void setExclusiveOwnerThread(Thread t) {
74 exclusiveOwnerThread = t;
75 }
76
77 /**
78 * Returns the thread last set by
79 * <tt>setExclusiveOwnerThread</tt>, or <tt>null</tt> if never
80 * set. This method does not otherwise impose any synchronization
81 * or <tt>volatile</tt> field accesses.
82 * @return the owner thread
83 */
84 protected final Thread getExclusiveOwnerThread() {
85 return exclusiveOwnerThread;
86 }
87 }
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