The
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
ReentrantLock
.
The
ReadWriteLock
interface
similarly defines locks that may be shared among readers but are
exclusive to writers. Only a single implementation,
ReentrantReadWriteLock
, is provided, since
it covers most standard usage contexts. But programmers may create
their own implementations to cover nonstandard requirements.
The
Condition
interface
describes condition variables that may be associated with Locks.
These are similar in usage to the implicit monitors accessed using
Object.wait
, but offer extended capabilities.
In particular, multiple
Condition
objects may be associated
with a single
Lock
. To avoid compatibility issues, the
names of
Condition
methods are different from the
corresponding
Object
versions.
The
AbstractQueuedSynchronizer
class serves as a useful superclass for defining locks and other
synchronizers that rely on queuing blocked threads. The
AbstractQueuedLongSynchronizer
class
provides the same functionality but extends support to 64 bits of
synchronization state. Both extend class
AbstractOwnableSynchronizer
, a simple
class that helps record the thread currently holding exclusive
synchronization. The
LockSupport
class provides lower-level blocking and unblocking support that is
useful for those developers implementing their own customized lock
classes.
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.
|
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
readLock()
.
|
ReentrantReadWriteLock.WriteLock |
The lock returned by method
writeLock()
.
|