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/*

 * 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/

 */

/**

 * Interfaces and classes providing a framework for locking and waiting

 * for conditions that is distinct from built-in synchronization and

 * monitors.  The framework permits much greater flexibility in the use of

 * locks and conditions, at the expense of more awkward syntax.

 *

 * <p>The {@link java.util.concurrent.locks.Lock} interface supports

 * locking disciplines that differ in semantics (reentrant, fair, etc),

 * and that can be used in non-block-structured contexts including

 * hand-over-hand and lock reordering algorithms.  The main implementation

 * is {@link java.util.concurrent.locks.ReentrantLock}.

 *

 * <p>The {@link java.util.concurrent.locks.ReadWriteLock} interface

 * similarly defines locks that may be shared among readers but are

 * exclusive to writers.  Only a single implementation, {@link

 * java.util.concurrent.locks.ReentrantReadWriteLock}, is provided, since

 * it covers most standard usage contexts.  But programmers may create

 * their own implementations to cover nonstandard requirements.

 *

 * <p>The {@link java.util.concurrent.locks.Condition} interface

 * describes condition variables that may be associated with Locks.

 * These are similar in usage to the implicit monitors accessed using

 * {@code Object.wait}, but offer extended capabilities.

 * In particular, multiple {@code Condition} objects may be associated

 * with a single {@code Lock}.  To avoid compatibility issues, the

 * names of {@code Condition} methods are different from the

 * corresponding {@code Object} versions.

 *

 * <p>The {@link java.util.concurrent.locks.AbstractQueuedSynchronizer}

 * class serves as a useful superclass for defining locks and other

 * synchronizers that rely on queuing blocked threads.  The {@link

 * java.util.concurrent.locks.AbstractQueuedLongSynchronizer} class

 * provides the same functionality but extends support to 64 bits of

 * synchronization state.  Both extend class {@link

 * java.util.concurrent.locks.AbstractOwnableSynchronizer}, a simple

 * class that helps record the thread currently holding exclusive

 * synchronization.  The {@link java.util.concurrent.locks.LockSupport}

 * class provides lower-level blocking and unblocking support that is

 * useful for those developers implementing their own customized lock

 * classes.

 *

 * @since 1.5

 */

package java.util.concurrent.locks;