AbstractQueuedLongSynchronizer (Java SE 9 & JDK 9 ) (original) (raw)
Constructor Detail
* #### AbstractQueuedLongSynchronizer
protected AbstractQueuedLongSynchronizer()
Creates a new `AbstractQueuedLongSynchronizer` instance with initial synchronization state of zero.
Method Detail
* #### getState
protected final long getState()
Returns the current value of synchronization state. This operation has memory semantics of a `volatile` read.
Returns:
current state value
* #### setState
protected final void setState(long newState)
Sets the value of synchronization state. This operation has memory semantics of a `volatile` write.
Parameters:
`newState` \- the new state value
* #### compareAndSetState
protected final boolean compareAndSetState(long expect,
long update)
Atomically sets synchronization state to the given updated value if the current state value equals the expected value. This operation has memory semantics of a `volatile` read and write.
Parameters:
`expect` \- the expected value
`update` \- the new value
Returns:
`true` if successful. False return indicates that the actual value was not equal to the expected value.
* #### tryAcquire
protected boolean tryAcquire(long arg)
Attempts to acquire in exclusive mode. This method should query if the state of the object permits it to be acquired in the exclusive mode, and if so to acquire it.
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()](../../../../java/util/concurrent/locks/Lock.html#tryLock--).
The default implementation throws [UnsupportedOperationException](../../../../java/lang/UnsupportedOperationException.html "class in java.lang").
Parameters:
`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.
Returns:
`true` if successful. Upon success, this object has been acquired.
Throws:
`[IllegalMonitorStateException](../../../../java/lang/IllegalMonitorStateException.html "class in java.lang")` \- 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](../../../../java/lang/UnsupportedOperationException.html "class in java.lang")` \- if exclusive mode is not supported
* #### tryRelease
protected boolean tryRelease(long arg)
Attempts to set the state to reflect a release in exclusive mode.
This method is always invoked by the thread performing release.
The default implementation throws[UnsupportedOperationException](../../../../java/lang/UnsupportedOperationException.html "class in java.lang").
Parameters:
`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.
Returns:
`true` if this object is now in a fully released state, so that any waiting threads may attempt to acquire; and `false` otherwise.
Throws:
`[IllegalMonitorStateException](../../../../java/lang/IllegalMonitorStateException.html "class in java.lang")` \- 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](../../../../java/lang/UnsupportedOperationException.html "class in java.lang")` \- if exclusive mode is not supported
* #### tryAcquireShared
protected long tryAcquireShared(long arg)
Attempts to acquire in shared mode. This method should query if the state of the object permits it to be acquired in the shared mode, and if so to acquire it.
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.
The default implementation throws [UnsupportedOperationException](../../../../java/lang/UnsupportedOperationException.html "class in java.lang").
Parameters:
`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.
Returns:
a negative value on failure; zero if acquisition in shared mode succeeded but no subsequent shared-mode acquire can succeed; and a positive value if acquisition in shared mode succeeded and subsequent shared-mode acquires might also succeed, in which case a subsequent waiting thread must check availability. (Support for three different return values enables this method to be used in contexts where acquires only sometimes act exclusively.) Upon success, this object has been acquired.
Throws:
`[IllegalMonitorStateException](../../../../java/lang/IllegalMonitorStateException.html "class in java.lang")` \- 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](../../../../java/lang/UnsupportedOperationException.html "class in java.lang")` \- if shared mode is not supported
* #### tryReleaseShared
protected boolean tryReleaseShared(long arg)
Attempts to set the state to reflect a release in shared mode.
This method is always invoked by the thread performing release.
The default implementation throws[UnsupportedOperationException](../../../../java/lang/UnsupportedOperationException.html "class in java.lang").
Parameters:
`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.
Returns:
`true` if this release of shared mode may permit a waiting acquire (shared or exclusive) to succeed; and`false` otherwise
Throws:
`[IllegalMonitorStateException](../../../../java/lang/IllegalMonitorStateException.html "class in java.lang")` \- 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](../../../../java/lang/UnsupportedOperationException.html "class in java.lang")` \- if shared mode is not supported
* #### isHeldExclusively
protected boolean isHeldExclusively()
Returns:
`true` if synchronization is held exclusively;`false` otherwise
Throws:
`[UnsupportedOperationException](../../../../java/lang/UnsupportedOperationException.html "class in java.lang")` \- if conditions are not supported
* #### acquire
public final void acquire(long arg)
Acquires in exclusive mode, ignoring interrupts. Implemented by invoking at least once [tryAcquire(long)](../../../../java/util/concurrent/locks/AbstractQueuedLongSynchronizer.html#tryAcquire-long-), returning on success. Otherwise the thread is queued, possibly repeatedly blocking and unblocking, invoking [tryAcquire(long)](../../../../java/util/concurrent/locks/AbstractQueuedLongSynchronizer.html#tryAcquire-long-) until success. This method can be used to implement method [Lock.lock()](../../../../java/util/concurrent/locks/Lock.html#lock--).
Parameters:
`arg` \- the acquire argument. This value is conveyed to[tryAcquire(long)](../../../../java/util/concurrent/locks/AbstractQueuedLongSynchronizer.html#tryAcquire-long-) but is otherwise uninterpreted and can represent anything you like.
* #### acquireInterruptibly
public final void acquireInterruptibly(long arg)
throws [InterruptedException](../../../../java/lang/InterruptedException.html "class in java.lang")
Acquires in exclusive mode, aborting if interrupted. Implemented by first checking interrupt status, then invoking at least once [tryAcquire(long)](../../../../java/util/concurrent/locks/AbstractQueuedLongSynchronizer.html#tryAcquire-long-), returning on success. Otherwise the thread is queued, possibly repeatedly blocking and unblocking, invoking [tryAcquire(long)](../../../../java/util/concurrent/locks/AbstractQueuedLongSynchronizer.html#tryAcquire-long-) until success or the thread is interrupted. This method can be used to implement method [Lock.lockInterruptibly()](../../../../java/util/concurrent/locks/Lock.html#lockInterruptibly--).
Parameters:
`arg` \- the acquire argument. This value is conveyed to[tryAcquire(long)](../../../../java/util/concurrent/locks/AbstractQueuedLongSynchronizer.html#tryAcquire-long-) but is otherwise uninterpreted and can represent anything you like.
Throws:
`[InterruptedException](../../../../java/lang/InterruptedException.html "class in java.lang")` \- if the current thread is interrupted
* #### tryAcquireNanos
public final boolean tryAcquireNanos(long arg,
long nanosTimeout)
throws [InterruptedException](../../../../java/lang/InterruptedException.html "class in java.lang")
Attempts to acquire in exclusive mode, aborting if interrupted, and failing if the given timeout elapses. Implemented by first checking interrupt status, then invoking at least once [tryAcquire(long)](../../../../java/util/concurrent/locks/AbstractQueuedLongSynchronizer.html#tryAcquire-long-), returning on success. Otherwise, the thread is queued, possibly repeatedly blocking and unblocking, invoking[tryAcquire(long)](../../../../java/util/concurrent/locks/AbstractQueuedLongSynchronizer.html#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)](../../../../java/util/concurrent/locks/Lock.html#tryLock-long-java.util.concurrent.TimeUnit-).
Parameters:
`arg` \- the acquire argument. This value is conveyed to[tryAcquire(long)](../../../../java/util/concurrent/locks/AbstractQueuedLongSynchronizer.html#tryAcquire-long-) but is otherwise uninterpreted and can represent anything you like.
`nanosTimeout` \- the maximum number of nanoseconds to wait
Returns:
`true` if acquired; `false` if timed out
Throws:
`[InterruptedException](../../../../java/lang/InterruptedException.html "class in java.lang")` \- if the current thread is interrupted
* #### release
public final boolean release(long arg)
Releases in exclusive mode. Implemented by unblocking one or more threads if [tryRelease(long)](../../../../java/util/concurrent/locks/AbstractQueuedLongSynchronizer.html#tryRelease-long-) returns true. This method can be used to implement method [Lock.unlock()](../../../../java/util/concurrent/locks/Lock.html#unlock--).
Parameters:
`arg` \- the release argument. This value is conveyed to[tryRelease(long)](../../../../java/util/concurrent/locks/AbstractQueuedLongSynchronizer.html#tryRelease-long-) but is otherwise uninterpreted and can represent anything you like.
Returns:
the value returned from [tryRelease(long)](../../../../java/util/concurrent/locks/AbstractQueuedLongSynchronizer.html#tryRelease-long-)
* #### acquireShared
public final void acquireShared(long arg)
Acquires in shared mode, ignoring interrupts. Implemented by first invoking at least once [tryAcquireShared(long)](../../../../java/util/concurrent/locks/AbstractQueuedLongSynchronizer.html#tryAcquireShared-long-), returning on success. Otherwise the thread is queued, possibly repeatedly blocking and unblocking, invoking [tryAcquireShared(long)](../../../../java/util/concurrent/locks/AbstractQueuedLongSynchronizer.html#tryAcquireShared-long-) until success.
Parameters:
`arg` \- the acquire argument. This value is conveyed to[tryAcquireShared(long)](../../../../java/util/concurrent/locks/AbstractQueuedLongSynchronizer.html#tryAcquireShared-long-) but is otherwise uninterpreted and can represent anything you like.
* #### acquireSharedInterruptibly
public final void acquireSharedInterruptibly(long arg)
throws [InterruptedException](../../../../java/lang/InterruptedException.html "class in java.lang")
Acquires in shared mode, aborting if interrupted. Implemented by first checking interrupt status, then invoking at least once[tryAcquireShared(long)](../../../../java/util/concurrent/locks/AbstractQueuedLongSynchronizer.html#tryAcquireShared-long-), returning on success. Otherwise the thread is queued, possibly repeatedly blocking and unblocking, invoking [tryAcquireShared(long)](../../../../java/util/concurrent/locks/AbstractQueuedLongSynchronizer.html#tryAcquireShared-long-) until success or the thread is interrupted.
Parameters:
`arg` \- the acquire argument. This value is conveyed to [tryAcquireShared(long)](../../../../java/util/concurrent/locks/AbstractQueuedLongSynchronizer.html#tryAcquireShared-long-) but is otherwise uninterpreted and can represent anything you like.
Throws:
`[InterruptedException](../../../../java/lang/InterruptedException.html "class in java.lang")` \- if the current thread is interrupted
* #### tryAcquireSharedNanos
public final boolean tryAcquireSharedNanos(long arg,
long nanosTimeout)
throws [InterruptedException](../../../../java/lang/InterruptedException.html "class in java.lang")
Attempts to acquire in shared mode, aborting if interrupted, and failing if the given timeout elapses. Implemented by first checking interrupt status, then invoking at least once [tryAcquireShared(long)](../../../../java/util/concurrent/locks/AbstractQueuedLongSynchronizer.html#tryAcquireShared-long-), returning on success. Otherwise, the thread is queued, possibly repeatedly blocking and unblocking, invoking [tryAcquireShared(long)](../../../../java/util/concurrent/locks/AbstractQueuedLongSynchronizer.html#tryAcquireShared-long-) until success or the thread is interrupted or the timeout elapses.
Parameters:
`arg` \- the acquire argument. This value is conveyed to[tryAcquireShared(long)](../../../../java/util/concurrent/locks/AbstractQueuedLongSynchronizer.html#tryAcquireShared-long-) but is otherwise uninterpreted and can represent anything you like.
`nanosTimeout` \- the maximum number of nanoseconds to wait
Returns:
`true` if acquired; `false` if timed out
Throws:
`[InterruptedException](../../../../java/lang/InterruptedException.html "class in java.lang")` \- if the current thread is interrupted
* #### releaseShared
public final boolean releaseShared(long arg)
Releases in shared mode. Implemented by unblocking one or more threads if [tryReleaseShared(long)](../../../../java/util/concurrent/locks/AbstractQueuedLongSynchronizer.html#tryReleaseShared-long-) returns true.
Parameters:
`arg` \- the release argument. This value is conveyed to[tryReleaseShared(long)](../../../../java/util/concurrent/locks/AbstractQueuedLongSynchronizer.html#tryReleaseShared-long-) but is otherwise uninterpreted and can represent anything you like.
Returns:
the value returned from [tryReleaseShared(long)](../../../../java/util/concurrent/locks/AbstractQueuedLongSynchronizer.html#tryReleaseShared-long-)
* #### hasQueuedThreads
public final boolean hasQueuedThreads()
Queries whether any threads are waiting to acquire. Note that because cancellations due to interrupts and timeouts may occur at any time, a `true` return does not guarantee that any other thread will ever acquire.
In this implementation, this operation returns in constant time.
Returns:
`true` if there may be other threads waiting to acquire
* #### hasContended
public final boolean hasContended()
Queries whether any threads have ever contended to acquire this synchronizer; that is, if an acquire method has ever blocked.
In this implementation, this operation returns in constant time.
Returns:
`true` if there has ever been contention
* #### getFirstQueuedThread
public final [Thread](../../../../java/lang/Thread.html "class in java.lang") getFirstQueuedThread()
Returns the first (longest-waiting) thread in the queue, or`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.
Returns:
the first (longest-waiting) thread in the queue, or`null` if no threads are currently queued
* #### isQueued
public final boolean isQueued([Thread](../../../../java/lang/Thread.html "class in java.lang") thread)
Returns true if the given thread is currently queued.
This implementation traverses the queue to determine presence of the given thread.
Parameters:
`thread` \- the thread
Returns:
`true` if the given thread is on the queue
Throws:
`[NullPointerException](../../../../java/lang/NullPointerException.html "class in java.lang")` \- if the thread is null
* #### hasQueuedPredecessors
public final boolean hasQueuedPredecessors()
Queries whether any threads have been waiting to acquire longer than the current thread.
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](AbstractQueuedSynchronizer.html#barging). Such a synchronizer's [tryAcquire(long)](../../../../java/util/concurrent/locks/AbstractQueuedLongSynchronizer.html#tryAcquire-long-) method should return`false`, and its [tryAcquireShared(long)](../../../../java/util/concurrent/locks/AbstractQueuedLongSynchronizer.html#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(int arg) {
if (isHeldExclusively()) {
// A reentrant acquire; increment hold count
return true;
} else if (hasQueuedPredecessors()) {
return false;
} else {
// try to acquire normally
}
}`
Returns:
`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 empty
Since:
1.7
* #### getQueueLength
public final int getQueueLength()
Returns an estimate of the number of threads waiting to acquire. The value is only an estimate because the number of threads may change dynamically while this method traverses internal data structures. This method is designed for use in monitoring system state, not for synchronization control.
Returns:
the estimated number of threads waiting to acquire
* #### getQueuedThreads
public final [Collection](../../../../java/util/Collection.html "interface in java.util")<[Thread](../../../../java/lang/Thread.html "class in java.lang")> getQueuedThreads()
Returns a collection containing threads that may be waiting to acquire. Because the actual set of threads may change dynamically while constructing this result, the returned collection is only a best-effort estimate. The elements of the returned collection are in no particular order. This method is designed to facilitate construction of subclasses that provide more extensive monitoring facilities.
Returns:
the collection of threads
* #### getExclusiveQueuedThreads
public final [Collection](../../../../java/util/Collection.html "interface in java.util")<[Thread](../../../../java/lang/Thread.html "class in java.lang")> getExclusiveQueuedThreads()
Returns a collection containing threads that may be waiting to acquire in exclusive mode. This has the same properties as [getQueuedThreads()](../../../../java/util/concurrent/locks/AbstractQueuedLongSynchronizer.html#getQueuedThreads--) except that it only returns those threads waiting due to an exclusive acquire.
Returns:
the collection of threads
* #### getSharedQueuedThreads
public final [Collection](../../../../java/util/Collection.html "interface in java.util")<[Thread](../../../../java/lang/Thread.html "class in java.lang")> getSharedQueuedThreads()
Returns a collection containing threads that may be waiting to acquire in shared mode. This has the same properties as [getQueuedThreads()](../../../../java/util/concurrent/locks/AbstractQueuedLongSynchronizer.html#getQueuedThreads--) except that it only returns those threads waiting due to a shared acquire.
Returns:
the collection of threads
* #### toString
public [String](../../../../java/lang/String.html "class in java.lang") toString()
Returns a string identifying this synchronizer, as well as its state. The state, in brackets, includes the String `"State ="` followed by the current value of [getState()](../../../../java/util/concurrent/locks/AbstractQueuedLongSynchronizer.html#getState--), and either`"nonempty"` or `"empty"` depending on whether the queue is empty.
Overrides:
`[toString](../../../../java/lang/Object.html#toString--)` in class `[Object](../../../../java/lang/Object.html "class in java.lang")`
Returns:
a string identifying this synchronizer, as well as its state
* #### owns
public final boolean owns([AbstractQueuedLongSynchronizer.ConditionObject](../../../../java/util/concurrent/locks/AbstractQueuedLongSynchronizer.ConditionObject.html "class in java.util.concurrent.locks") condition)
Queries whether the given ConditionObject uses this synchronizer as its lock.
Parameters:
`condition` \- the condition
Returns:
`true` if owned
Throws:
`[NullPointerException](../../../../java/lang/NullPointerException.html "class in java.lang")` \- if the condition is null
* #### hasWaiters
public final boolean hasWaiters([AbstractQueuedLongSynchronizer.ConditionObject](../../../../java/util/concurrent/locks/AbstractQueuedLongSynchronizer.ConditionObject.html "class in java.util.concurrent.locks") condition)
Queries whether any threads are waiting on the given condition associated with this synchronizer. Note that because timeouts and interrupts may occur at any time, a `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.
Parameters:
`condition` \- the condition
Returns:
`true` if there are any waiting threads
Throws:
`[IllegalMonitorStateException](../../../../java/lang/IllegalMonitorStateException.html "class in java.lang")` \- if exclusive synchronization is not held
`[IllegalArgumentException](../../../../java/lang/IllegalArgumentException.html "class in java.lang")` \- if the given condition is not associated with this synchronizer
`[NullPointerException](../../../../java/lang/NullPointerException.html "class in java.lang")` \- if the condition is null
* #### getWaitQueueLength
public final int getWaitQueueLength([AbstractQueuedLongSynchronizer.ConditionObject](../../../../java/util/concurrent/locks/AbstractQueuedLongSynchronizer.ConditionObject.html "class in java.util.concurrent.locks") condition)
Returns an estimate of the number of threads waiting on the given condition associated with this synchronizer. Note that because timeouts and interrupts may occur at any time, the estimate serves only as an upper bound on the actual number of waiters. This method is designed for use in monitoring system state, not for synchronization control.
Parameters:
`condition` \- the condition
Returns:
the estimated number of waiting threads
Throws:
`[IllegalMonitorStateException](../../../../java/lang/IllegalMonitorStateException.html "class in java.lang")` \- if exclusive synchronization is not held
`[IllegalArgumentException](../../../../java/lang/IllegalArgumentException.html "class in java.lang")` \- if the given condition is not associated with this synchronizer
`[NullPointerException](../../../../java/lang/NullPointerException.html "class in java.lang")` \- if the condition is null
* #### getWaitingThreads
public final [Collection](../../../../java/util/Collection.html "interface in java.util")<[Thread](../../../../java/lang/Thread.html "class in java.lang")> getWaitingThreads([AbstractQueuedLongSynchronizer.ConditionObject](../../../../java/util/concurrent/locks/AbstractQueuedLongSynchronizer.ConditionObject.html "class in java.util.concurrent.locks") condition)
Returns a collection containing those threads that may be waiting on the given condition associated with this synchronizer. Because the actual set of threads may change dynamically while constructing this result, the returned collection is only a best-effort estimate. The elements of the returned collection are in no particular order.
Parameters:
`condition` \- the condition
Returns:
the collection of threads
Throws:
`[IllegalMonitorStateException](../../../../java/lang/IllegalMonitorStateException.html "class in java.lang")` \- if exclusive synchronization is not held
`[IllegalArgumentException](../../../../java/lang/IllegalArgumentException.html "class in java.lang")` \- if the given condition is not associated with this synchronizer
`[NullPointerException](../../../../java/lang/NullPointerException.html "class in java.lang")` \- if the condition is null