/*

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

 *

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

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

 * published by the Free Software Foundation.  Oracle designates this

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

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

 *

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

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

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

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

 * accompanied this code).

 *

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

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

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

 *

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

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

 * questions.

 */

/*

 * This file is available under and governed by the GNU General Public

 * License version 2 only, as published by the Free Software Foundation.

 * However, the following notice accompanied the original version of this

 * file:

 *

 * Written by Doug Lea with assistance from members of JCP JSR-166

 * Expert Group and released to the public domain, as explained at

 * http://creativecommons.org/publicdomain/zero/1.0/

 */

package java.util.concurrent.locks;

/**

 * A synchronizer that may be exclusively owned by a thread.  This

 * class provides a basis for creating locks and related synchronizers

 * that may entail a notion of ownership.  The

 * {@code AbstractOwnableSynchronizer} class itself does not manage or

 * use this information. However, subclasses and tools may use

 * appropriately maintained values to help control and monitor access

 * and provide diagnostics.

 *

 * @since 1.6

 * @author Doug Lea

 */

public abstract class AbstractOwnableSynchronizer

    implements java.io.Serializable {

    /** Use serial ID even though all fields transient. */

    private static final long serialVersionUID = 3737899427754241961L;

    /**

     * Empty constructor for use by subclasses.

     */

    protected AbstractOwnableSynchronizer() { }

    /**

     * The current owner of exclusive mode synchronization.

     */

    private transient Thread exclusiveOwnerThread;

    /**

     * Sets the thread that currently owns exclusive access.

     * A {@code null} argument indicates that no thread owns access.

     * This method does not otherwise impose any synchronization or

     * {@code volatile} field accesses.

     * @param thread the owner thread

     */

    protected final void setExclusiveOwnerThread(Thread thread) {

        exclusiveOwnerThread = thread;

    }

    /**

     * Returns the thread last set by {@code setExclusiveOwnerThread},

     * or {@code null} if never set.  This method does not otherwise

     * impose any synchronization or {@code volatile} field accesses.

     * @return the owner thread

     */

    protected final Thread getExclusiveOwnerThread() {

        return exclusiveOwnerThread;

    }

}