Added in API level 1

java.util.concurrent.locks

Interfaces

Condition Condition factors out the Object monitor methods (wait, notify and notifyAll) into distinct objects to give the effect of having multiple wait-sets per object, by combining them with the use of arbitrary Lock implementations. 
Lock Lock implementations provide more extensive locking operations than can be obtained using synchronized methods and statements. 
ReadWriteLock A ReadWriteLock maintains a pair of associated locks, one for read-only operations and one for writing. 

Classes

AbstractOwnableSynchronizer A synchronizer that may be exclusively owned by a thread. 
AbstractQueuedLongSynchronizer A version of AbstractQueuedSynchronizer in which synchronization state is maintained as a long. 
AbstractQueuedLongSynchronizer.ConditionObject Condition implementation for a AbstractQueuedLongSynchronizer serving as the basis of a Lock implementation. 
AbstractQueuedSynchronizer Provides a framework for implementing blocking locks and related synchronizers (semaphores, events, etc) that rely on first-in-first-out (FIFO) wait queues. 
AbstractQueuedSynchronizer.ConditionObject Condition implementation for a AbstractQueuedSynchronizer serving as the basis of a Lock implementation. 
LockSupport Basic thread blocking primitives for creating locks and other synchronization classes. 
ReentrantLock A reentrant mutual exclusion Lock with the same basic behavior and semantics as the implicit monitor lock accessed using synchronized methods and statements, but with extended capabilities. 
ReentrantReadWriteLock An implementation of ReadWriteLock supporting similar semantics to ReentrantLock. 
ReentrantReadWriteLock.ReadLock The lock returned by method ReentrantReadWriteLock#readLock. 
ReentrantReadWriteLock.WriteLock The lock returned by method ReentrantReadWriteLock#writeLock. 
StampedLock A capability-based lock with three modes for controlling read/write access.