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/*

 * 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/licenses/publicdomain

 */

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

 * <tt>AbstractOwnableSynchronizer</tt> 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

     * <tt>null</tt> argument indicates that no thread owns access.

     * This method does not otherwise impose any synchronization or

     * <tt>volatile</tt> field accesses.

     */

    protected final void setExclusiveOwnerThread(Thread t) {

        exclusiveOwnerThread = t;

    }

    /**

     * Returns the thread last set by

     * <tt>setExclusiveOwnerThread</tt>, or <tt>null</tt> if never

     * set.  This method does not otherwise impose any synchronization

     * or <tt>volatile</tt> field accesses.

     * @return the owner thread

     */

    protected final Thread getExclusiveOwnerThread() {

        return exclusiveOwnerThread;

    }

}