content: /*
   * 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;
      }
  }
  