ReentrantReadWriteLock.WriteLock (Java SE 9 & JDK 9 ) (original) (raw)
Constructor Detail
* #### WriteLock
protected WriteLock([ReentrantReadWriteLock](../../../../java/util/concurrent/locks/ReentrantReadWriteLock.html "class in java.util.concurrent.locks") lock)
Constructor for use by subclasses.
Parameters:
`lock` \- the outer lock object
Throws:
`[NullPointerException](../../../../java/lang/NullPointerException.html "class in java.lang")` \- if the lock is null
Method Detail
* #### lock
public void lock()
Acquires the write lock.
Acquires the write lock if neither the read nor write lock are held by another thread and returns immediately, setting the write lock hold count to one.
If the current thread already holds the write lock then the hold count is incremented by one and the method returns immediately.
If the lock is held by another thread then the current thread becomes disabled for thread scheduling purposes and lies dormant until the write lock has been acquired, at which time the write lock hold count is set to one.
Specified by:
`[lock](../../../../java/util/concurrent/locks/Lock.html#lock--)` in interface `[Lock](../../../../java/util/concurrent/locks/Lock.html "interface in java.util.concurrent.locks")`
* #### lockInterruptibly
public void lockInterruptibly()
throws [InterruptedException](../../../../java/lang/InterruptedException.html "class in java.lang")
Acquires the write lock unless the current thread is[interrupted](../../../../java/lang/Thread.html#interrupt--).
Acquires the write lock if neither the read nor write lock are held by another thread and returns immediately, setting the write lock hold count to one.
If the current thread already holds this lock then the hold count is incremented by one and the method returns immediately.
If the lock is held by another thread then the current thread becomes disabled for thread scheduling purposes and lies dormant until one of two things happens:
* The write lock is acquired by the current thread; or
* Some other thread [interrupts](../../../../java/lang/Thread.html#interrupt--) the current thread.
If the write lock is acquired by the current thread then the lock hold count is set to one.
If the current thread:
* has its interrupted status set on entry to this method; or
* is [interrupted](../../../../java/lang/Thread.html#interrupt--) while acquiring the write lock,
then [InterruptedException](../../../../java/lang/InterruptedException.html "class in java.lang") is thrown and the current thread's interrupted status is cleared.
In this implementation, as this method is an explicit interruption point, preference is given to responding to the interrupt over normal or reentrant acquisition of the lock.
Specified by:
`[lockInterruptibly](../../../../java/util/concurrent/locks/Lock.html#lockInterruptibly--)` in interface `[Lock](../../../../java/util/concurrent/locks/Lock.html "interface in java.util.concurrent.locks")`
Throws:
`[InterruptedException](../../../../java/lang/InterruptedException.html "class in java.lang")` \- if the current thread is interrupted
* #### tryLock
public boolean tryLock()
Acquires the write lock only if it is not held by another thread at the time of invocation.
Acquires the write lock if neither the read nor write lock are held by another thread and returns immediately with the value `true`, setting the write lock hold count to one. Even when this lock has been set to use a fair ordering policy, a call to`tryLock()` _will_ immediately acquire the lock if it is available, whether or not other threads are currently waiting for the write lock. This "barging" behavior can be useful in certain circumstances, even though it breaks fairness. If you want to honor the fairness setting for this lock, then use [tryLock(0, TimeUnit.SECONDS) ](../../../../java/util/concurrent/locks/ReentrantReadWriteLock.WriteLock.html#tryLock-long-java.util.concurrent.TimeUnit-) which is almost equivalent (it also detects interruption).
If the current thread already holds this lock then the hold count is incremented by one and the method returns`true`.
If the lock is held by another thread then this method will return immediately with the value `false`.
Specified by:
`[tryLock](../../../../java/util/concurrent/locks/Lock.html#tryLock--)` in interface `[Lock](../../../../java/util/concurrent/locks/Lock.html "interface in java.util.concurrent.locks")`
Returns:
`true` if the lock was free and was acquired by the current thread, or the write lock was already held by the current thread; and `false` otherwise.
* #### tryLock
public boolean tryLock(long timeout,
[TimeUnit](../../../../java/util/concurrent/TimeUnit.html "enum in java.util.concurrent") unit)
throws [InterruptedException](../../../../java/lang/InterruptedException.html "class in java.lang")
Acquires the write lock if it is not held by another thread within the given waiting time and the current thread has not been [interrupted](../../../../java/lang/Thread.html#interrupt--).
Acquires the write lock if neither the read nor write lock are held by another thread and returns immediately with the value `true`, setting the write lock hold count to one. If this lock has been set to use a fair ordering policy then an available lock_will not_ be acquired if any other threads are waiting for the write lock. This is in contrast to the [tryLock()](../../../../java/util/concurrent/locks/ReentrantReadWriteLock.WriteLock.html#tryLock--) method. If you want a timed `tryLock` that does permit barging on a fair lock then combine the timed and un-timed forms together:
`
if (lock.tryLock() ||
lock.tryLock(timeout, unit)) {
...
}`
If the current thread already holds this lock then the hold count is incremented by one and the method returns`true`.
If the lock is held by another thread then the current thread becomes disabled for thread scheduling purposes and lies dormant until one of three things happens:
* The write lock is acquired by the current thread; or
* Some other thread [interrupts](../../../../java/lang/Thread.html#interrupt--) the current thread; or
* The specified waiting time elapses
If the write lock is acquired then the value `true` is returned and the write lock hold count is set to one.
If the current thread:
* has its interrupted status set on entry to this method; or
* is [interrupted](../../../../java/lang/Thread.html#interrupt--) while acquiring the write lock,
then [InterruptedException](../../../../java/lang/InterruptedException.html "class in java.lang") is thrown and the current thread's interrupted status is cleared.
If the specified waiting time elapses then the value`false` is returned. If the time is less than or equal to zero, the method will not wait at all.
In this implementation, as this method is an explicit interruption point, preference is given to responding to the interrupt over normal or reentrant acquisition of the lock, and over reporting the elapse of the waiting time.
Specified by:
`[tryLock](../../../../java/util/concurrent/locks/Lock.html#tryLock-long-java.util.concurrent.TimeUnit-)` in interface `[Lock](../../../../java/util/concurrent/locks/Lock.html "interface in java.util.concurrent.locks")`
Parameters:
`timeout` \- the time to wait for the write lock
`unit` \- the time unit of the timeout argument
Returns:
`true` if the lock was free and was acquired by the current thread, or the write lock was already held by the current thread; and `false` if the waiting time elapsed before the lock could be acquired.
Throws:
`[InterruptedException](../../../../java/lang/InterruptedException.html "class in java.lang")` \- if the current thread is interrupted
`[NullPointerException](../../../../java/lang/NullPointerException.html "class in java.lang")` \- if the time unit is null
* #### unlock
public void unlock()
Attempts to release this lock.
If the current thread is the holder of this lock then the hold count is decremented. If the hold count is now zero then the lock is released. If the current thread is not the holder of this lock then [IllegalMonitorStateException](../../../../java/lang/IllegalMonitorStateException.html "class in java.lang") is thrown.
Specified by:
`[unlock](../../../../java/util/concurrent/locks/Lock.html#unlock--)` in interface `[Lock](../../../../java/util/concurrent/locks/Lock.html "interface in java.util.concurrent.locks")`
Throws:
`[IllegalMonitorStateException](../../../../java/lang/IllegalMonitorStateException.html "class in java.lang")` \- if the current thread does not hold this lock
* #### newCondition
public [Condition](../../../../java/util/concurrent/locks/Condition.html "interface in java.util.concurrent.locks") newCondition()
Returns a [Condition](../../../../java/util/concurrent/locks/Condition.html "interface in java.util.concurrent.locks") instance for use with this[Lock](../../../../java/util/concurrent/locks/Lock.html "interface in java.util.concurrent.locks") instance.
The returned [Condition](../../../../java/util/concurrent/locks/Condition.html "interface in java.util.concurrent.locks") instance supports the same usages as do the [Object](../../../../java/lang/Object.html "class in java.lang") monitor methods ([wait](../../../../java/lang/Object.html#wait--), [notify](../../../../java/lang/Object.html#notify--), and [notifyAll](../../../../java/lang/Object.html#notifyAll--)) when used with the built-in monitor lock.
* If this write lock is not held when any [Condition](../../../../java/util/concurrent/locks/Condition.html "interface in java.util.concurrent.locks") method is called then an [IllegalMonitorStateException](../../../../java/lang/IllegalMonitorStateException.html "class in java.lang") is thrown. (Read locks are held independently of write locks, so are not checked or affected. However it is essentially always an error to invoke a condition waiting method when the current thread has also acquired read locks, since other threads that could unblock it will not be able to acquire the write lock.)
* When the condition [waiting](../../../../java/util/concurrent/locks/Condition.html#await--) methods are called the write lock is released and, before they return, the write lock is reacquired and the lock hold count restored to what it was when the method was called.
* If a thread is [interrupted](../../../../java/lang/Thread.html#interrupt--) while waiting then the wait will terminate, an [InterruptedException](../../../../java/lang/InterruptedException.html "class in java.lang") will be thrown, and the thread's interrupted status will be cleared.
* Waiting threads are signalled in FIFO order.
* The ordering of lock reacquisition for threads returning from waiting methods is the same as for threads initially acquiring the lock, which is in the default case not specified, but for _fair_ locks favors those threads that have been waiting the longest.
Specified by:
`[newCondition](../../../../java/util/concurrent/locks/Lock.html#newCondition--)` in interface `[Lock](../../../../java/util/concurrent/locks/Lock.html "interface in java.util.concurrent.locks")`
Returns:
the Condition object
* #### toString
public [String](../../../../java/lang/String.html "class in java.lang") toString()
Returns a string identifying this lock, as well as its lock state. The state, in brackets includes either the String`"Unlocked"` or the String `"Locked by"` followed by the [name](../../../../java/lang/Thread.html#getName--) of the owning thread.
Overrides:
`[toString](../../../../java/lang/Object.html#toString--)` in class `[Object](../../../../java/lang/Object.html "class in java.lang")`
Returns:
a string identifying this lock, as well as its lock state
* #### isHeldByCurrentThread
public boolean isHeldByCurrentThread()
Returns:
`true` if the current thread holds this lock and`false` otherwise
Since:
1.6
* #### getHoldCount
public int getHoldCount()
Queries the number of holds on this write lock by the current thread. A thread has a hold on a lock for each lock action that is not matched by an unlock action. Identical in effect to [ReentrantReadWriteLock.getWriteHoldCount()](../../../../java/util/concurrent/locks/ReentrantReadWriteLock.html#getWriteHoldCount--).
Returns:
the number of holds on this lock by the current thread, or zero if this lock is not held by the current thread
Since:
1.6