Serializable
public abstract class AbstractQueuedLongSynchronizer extends AbstractOwnableSynchronizer implements Serializable
AbstractQueuedSynchronizer
in which synchronization state is maintained as a long
. This class has exactly the same structure, properties, and methods as AbstractQueuedSynchronizer
with the exception that all state-related parameters and results are defined as long
rather than int
. This class may be useful when creating synchronizers such as multilevel locks and barriers that require 64 bits of state. See AbstractQueuedSynchronizer
for usage notes and examples.
Modifier and Type | Class | Description |
---|---|---|
class |
AbstractQueuedLongSynchronizer.ConditionObject |
Condition implementation for a AbstractQueuedLongSynchronizer serving as the basis of a Lock implementation. |
Constructor | Description |
---|---|
AbstractQueuedLongSynchronizer() |
Constructor for subclasses to call. |
Modifier and Type | Method | Description |
---|---|---|
final void |
acquire |
Acquires in exclusive mode, ignoring interrupts. |
final void |
acquireInterruptibly |
Acquires in exclusive mode, aborting if interrupted. |
final void |
acquireShared |
Acquires in shared mode, ignoring interrupts. |
final void |
acquireSharedInterruptibly |
Acquires in shared mode, aborting if interrupted. |
protected final boolean |
compareAndSetState |
Atomically sets synchronization state to the given updated value if the current state value equals the expected value. |
final Collection |
getExclusiveQueuedThreads() |
Returns a collection containing threads that may be waiting to acquire in exclusive mode. |
final Thread |
getFirstQueuedThread() |
Returns the first (longest-waiting) thread in the queue, or null if no threads are currently queued. |
final Collection |
getQueuedThreads() |
Returns a collection containing threads that may be waiting to acquire. |
final int |
getQueueLength() |
Returns an estimate of the number of threads waiting to acquire. |
final Collection |
getSharedQueuedThreads() |
Returns a collection containing threads that may be waiting to acquire in shared mode. |
protected final long |
getState() |
Returns the current value of synchronization state. |
final Collection |
getWaitingThreads |
Returns a collection containing those threads that may be waiting on the given condition associated with this synchronizer. |
final int |
getWaitQueueLength |
Returns an estimate of the number of threads waiting on the given condition associated with this synchronizer. |
final boolean |
hasContended() |
Queries whether any threads have ever contended to acquire this synchronizer; that is, if an acquire method has ever blocked. |
final boolean |
hasQueuedPredecessors() |
Queries whether any threads have been waiting to acquire longer than the current thread. |
final boolean |
hasQueuedThreads() |
Queries whether any threads are waiting to acquire. |
final boolean |
hasWaiters |
Queries whether any threads are waiting on the given condition associated with this synchronizer. |
protected boolean |
isHeldExclusively() |
Returns true if synchronization is held exclusively with respect to the current (calling) thread. |
final boolean |
isQueued |
Returns true if the given thread is currently queued. |
final boolean |
owns |
Queries whether the given ConditionObject uses this synchronizer as its lock. |
final boolean |
release |
Releases in exclusive mode. |
final boolean |
releaseShared |
Releases in shared mode. |
protected final void |
setState |
Sets the value of synchronization state. |
String |
toString() |
Returns a string identifying this synchronizer, as well as its state. |
protected boolean |
tryAcquire |
Attempts to acquire in exclusive mode. |
final boolean |
tryAcquireNanos |
Attempts to acquire in exclusive mode, aborting if interrupted, and failing if the given timeout elapses. |
protected long |
tryAcquireShared |
Attempts to acquire in shared mode. |
final boolean |
tryAcquireSharedNanos |
Attempts to acquire in shared mode, aborting if interrupted, and failing if the given timeout elapses. |
protected boolean |
tryRelease |
Attempts to set the state to reflect a release in exclusive mode. |
protected boolean |
tryReleaseShared |
Attempts to set the state to reflect a release in shared mode. |
getExclusiveOwnerThread, setExclusiveOwnerThread
public AbstractQueuedLongSynchronizer()
protected final long getState()
volatile
read.protected final void setState(long newState)
volatile
write.newState
- the new state valueprotected final boolean compareAndSetState(long expect, long update)
volatile
read and write.expect
- the expected valueupdate
- the new valuetrue
if successful. False return indicates that the actual value was not equal to the expected value.protected boolean tryAcquire(long arg)
This method is always invoked by the thread performing acquire. If this method reports failure, the acquire method may queue the thread, if it is not already queued, until it is signalled by a release from some other thread. This can be used to implement method Lock.tryLock()
.
The default implementation throws UnsupportedOperationException
.
arg
- the acquire argument. This value is always the one passed to an acquire method, or is the value saved on entry to a condition wait. The value is otherwise uninterpreted and can represent anything you like.true
if successful. Upon success, this object has been acquired.IllegalMonitorStateException
- if acquiring would place this synchronizer in an illegal state. This exception must be thrown in a consistent fashion for synchronization to work correctly.UnsupportedOperationException
- if exclusive mode is not supportedprotected boolean tryRelease(long arg)
This method is always invoked by the thread performing release.
The default implementation throws UnsupportedOperationException
.
arg
- the release argument. This value is always the one passed to a release method, or the current state value upon entry to a condition wait. The value is otherwise uninterpreted and can represent anything you like.true
if this object is now in a fully released state, so that any waiting threads may attempt to acquire; and false
otherwise.IllegalMonitorStateException
- if releasing would place this synchronizer in an illegal state. This exception must be thrown in a consistent fashion for synchronization to work correctly.UnsupportedOperationException
- if exclusive mode is not supportedprotected boolean isHeldExclusively()
true
if synchronization is held exclusively with respect to the current (calling) thread. This method is invoked upon each call to a AbstractQueuedLongSynchronizer.ConditionObject
method. The default implementation throws UnsupportedOperationException
. This method is invoked internally only within AbstractQueuedLongSynchronizer.ConditionObject
methods, so need not be defined if conditions are not used.
true
if synchronization is held exclusively; false
otherwiseUnsupportedOperationException
- if conditions are not supportedpublic final void acquire(long arg)
tryAcquire(long)
, returning on success. Otherwise the thread is queued, possibly repeatedly blocking and unblocking, invoking tryAcquire(long)
until success. This method can be used to implement method Lock.lock()
.arg
- the acquire argument. This value is conveyed to tryAcquire(long)
but is otherwise uninterpreted and can represent anything you like.public final void acquireInterruptibly(long arg) throws InterruptedException
tryAcquire(long)
, returning on success. Otherwise the thread is queued, possibly repeatedly blocking and unblocking, invoking tryAcquire(long)
until success or the thread is interrupted. This method can be used to implement method Lock.lockInterruptibly()
.arg
- the acquire argument. This value is conveyed to tryAcquire(long)
but is otherwise uninterpreted and can represent anything you like.InterruptedException
- if the current thread is interruptedpublic final boolean tryAcquireNanos(long arg, long nanosTimeout) throws InterruptedException
tryAcquire(long)
, returning on success. Otherwise, the thread is queued, possibly repeatedly blocking and unblocking, invoking tryAcquire(long)
until success or the thread is interrupted or the timeout elapses. This method can be used to implement method Lock.tryLock(long, TimeUnit)
.arg
- the acquire argument. This value is conveyed to tryAcquire(long)
but is otherwise uninterpreted and can represent anything you like.nanosTimeout
- the maximum number of nanoseconds to waittrue
if acquired; false
if timed outInterruptedException
- if the current thread is interruptedpublic final boolean release(long arg)
tryRelease(long)
returns true. This method can be used to implement method Lock.unlock()
.arg
- the release argument. This value is conveyed to tryRelease(long)
but is otherwise uninterpreted and can represent anything you like.tryRelease(long)
public final boolean hasQueuedThreads()
true
return does not guarantee that any other thread will ever acquire.true
if there may be other threads waiting to acquirepublic final boolean hasContended()
In this implementation, this operation returns in constant time.
true
if there has ever been contentionpublic final Thread getFirstQueuedThread()
null
if no threads are currently queued. In this implementation, this operation normally returns in constant time, but may iterate upon contention if other threads are concurrently modifying the queue.
null
if no threads are currently queuedpublic final boolean isQueued(Thread thread)
This implementation traverses the queue to determine presence of the given thread.
thread
- the threadtrue
if the given thread is on the queueNullPointerException
- if the thread is nullpublic final boolean hasQueuedPredecessors()
An invocation of this method is equivalent to (but may be more efficient than):
getFirstQueuedThread() != Thread.currentThread()
&& hasQueuedThreads()
Note that because cancellations due to interrupts and timeouts may occur at any time, a true
return does not guarantee that some other thread will acquire before the current thread. Likewise, it is possible for another thread to win a race to enqueue after this method has returned false
, due to the queue being empty.
This method is designed to be used by a fair synchronizer to avoid barging. Such a synchronizer's tryAcquire(long)
method should return false
, and its tryAcquireShared(long)
method should return a negative value, if this method returns true
(unless this is a reentrant acquire). For example, the
tryAcquire
method for a fair, reentrant, exclusive mode synchronizer might look like this:
protected boolean tryAcquire(long arg) {
if (isHeldExclusively()) {
// A reentrant acquire; increment hold count
return true;
} else if (hasQueuedPredecessors()) {
return false;
} else {
// try to acquire normally
}
}
true
if there is a queued thread preceding the current thread, and false
if the current thread is at the head of the queue or the queue is emptypublic final int getQueueLength()
public final Collection<Thread> getQueuedThreads()
public final Collection<Thread> getExclusiveQueuedThreads()
getQueuedThreads()
except that it only returns those threads waiting due to an exclusive acquire.public String toString()
"State ="
followed by the current value of getState()
, and either "nonempty"
or "empty"
depending on whether the queue is empty.public final boolean owns(AbstractQueuedLongSynchronizer.ConditionObject condition)
condition
- the conditiontrue
if ownedNullPointerException
- if the condition is nullpublic final boolean hasWaiters(AbstractQueuedLongSynchronizer.ConditionObject condition)
true
return does not guarantee that a future signal
will awaken any threads. This method is designed primarily for use in monitoring of the system state.condition
- the conditiontrue
if there are any waiting threadsIllegalMonitorStateException
- if exclusive synchronization is not heldIllegalArgumentException
- if the given condition is not associated with this synchronizerNullPointerException
- if the condition is nullpublic final int getWaitQueueLength(AbstractQueuedLongSynchronizer.ConditionObject condition)
condition
- the conditionIllegalMonitorStateException
- if exclusive synchronization is not heldIllegalArgumentException
- if the given condition is not associated with this synchronizerNullPointerException
- if the condition is nullpublic final Collection<Thread> getWaitingThreads(AbstractQueuedLongSynchronizer.ConditionObject condition)
condition
- the conditionIllegalMonitorStateException
- if exclusive synchronization is not heldIllegalArgumentException
- if the given condition is not associated with this synchronizerNullPointerException
- if the condition is null
© 1993, 2023, Oracle and/or its affiliates. All rights reserved.
Documentation extracted from Debian's OpenJDK Development Kit package.
Licensed under the GNU General Public License, version 2, with the Classpath Exception.
Various third party code in OpenJDK is licensed under different licenses (see Debian package).
Java and OpenJDK are trademarks or registered trademarks of Oracle and/or its affiliates.
https://docs.oracle.com/en/java/javase/21/docs/api/java.base/java/util/concurrent/locks/AbstractQueuedLongSynchronizer.html