edu.emory.mathcs.backport.java.util.concurrent.locks

Class ReentrantReadWriteLock.WriteLock

public static class ReentrantReadWriteLock.WriteLock extends Object implements Lock, CondVar.ExclusiveLock, Serializable

The lock returned by method ReentrantReadWriteLock.
Constructor Summary
protected WriteLock(ReentrantReadWriteLock lock)
Constructor for use by subclasses
Method Summary
intgetHoldCount()
Queries the number of holds on this write lock by the current thread.
booleanisHeldByCurrentThread()
Queries if this write lock is held by the current thread.
voidlock()
Acquires the write lock.
voidlockInterruptibly()
Acquires the write lock unless the current thread is Thread#interrupt interrupted.
ConditionnewCondition()
Returns a Condition instance for use with this Lock instance.
StringtoString()
Returns a string identifying this lock, as well as its lock state.
booleantryLock()
Acquires the write lock only if it is not held by another thread at the time of invocation.
booleantryLock(long timeout, TimeUnit unit)
Acquires the write lock if it is not held by another thread within the given waiting time and the current thread has not been Thread#interrupt interrupted.
voidunlock()
Attempts to release this lock.

Constructor Detail

WriteLock

protected WriteLock(ReentrantReadWriteLock lock)
Constructor for use by subclasses

Parameters: lock the outer lock object

Throws: NullPointerException if the lock is null

Method Detail

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.

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

isHeldByCurrentThread

public boolean isHeldByCurrentThread()
Queries if this write lock is held by the current thread. Identical in effect to ReentrantReadWriteLock.

Returns: {@code true} if the current thread holds this lock and {@code false} otherwise

Since: 1.6

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.

lockInterruptibly

public void lockInterruptibly()
Acquires the write lock unless the current thread is Thread#interrupt interrupted.

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:

If the write lock is acquired by the current thread then the lock hold count is set to one.

If the current thread:

then InterruptedException 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.

Throws: InterruptedException if the current thread is interrupted

newCondition

public Condition newCondition()
Returns a Condition instance for use with this Lock instance.

The returned Condition instance supports the same usages as do the Object monitor methods ( Object#wait() wait, Object#notify notify, and Object#notifyAll notifyAll) when used with the built-in monitor lock.

Returns: the Condition object

toString

public String toString()
Returns a string identifying this lock, as well as its lock state. The state, in brackets includes either the String {@code "Unlocked"} or the String {@code "Locked by"} followed by the Thread#getName name of the owning thread.

Returns: a string identifying this lock, as well as its lock state

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 {@code 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 {@code 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) 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 {@code true}.

If the lock is held by another thread then this method will return immediately with the value {@code false}.

Returns: {@code 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 {@code false} otherwise.

tryLock

public boolean tryLock(long timeout, TimeUnit unit)
Acquires the write lock if it is not held by another thread within the given waiting time and the current thread has not been Thread#interrupt interrupted.

Acquires the write lock if neither the read nor write lock are held by another thread and returns immediately with the value {@code 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 method. If you want a timed {@code 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 {@code 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:

If the write lock is acquired then the value {@code true} is returned and the write lock hold count is set to one.

If the current thread:

then InterruptedException is thrown and the current thread's interrupted status is cleared.

If the specified waiting time elapses then the value {@code 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.

Parameters: timeout the time to wait for the write lock unit the time unit of the timeout argument

Returns: {@code 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 {@code false} if the waiting time elapsed before the lock could be acquired.

Throws: InterruptedException if the current thread is interrupted NullPointerException 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 is thrown.

Throws: IllegalMonitorStateException if the current thread does not hold this lock.