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java.lang.Object
edu.emory.mathcs.backport.java.util.concurrent.locks.ReentrantReadWriteLock.ReadLock
public static class ReentrantReadWriteLock.ReadLock
extends java.lang.Object
implements Lock, java.io.Serializable
ReentrantReadWriteLock.readLock()
.
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protected ReadLock(ReentrantReadWriteLock lock)
Constructor for use by subclasses
- Parameters:
lock
- the outer lock object
public void lock()
Acquires the read lock. Acquires the read lock if the write lock is not held by another thread and returns immediately. If the write lock is held by another thread then the current thread becomes disabled for thread scheduling purposes and lies dormant until the read lock has been acquired.
public void lockInterruptibly() throws InterruptedException
Acquires the read lock unless the current thread is interrupted. Acquires the read lock if the write lock is not held by another thread and returns immediately. If the write 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 current thread:
- The read lock is acquired by the current thread; or
- Some other thread interrupts the current thread.
then
- has its interrupted status set on entry to this method; or
- is interrupted while acquiring the read lock,
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.
- Specified by:
- lockInterruptibly in interface Lock
public Condition newCondition()
ThrowsUnsupportedOperationException
becauseReadLocks
do not support conditions.
- Specified by:
- newCondition in interface Lock
public String toString()
Returns a string identifying this lock, as well as its lock state. The state, in brackets, includes the String"Read locks ="
followed by the number of held read locks.
- Returns:
- a string identifying this lock, as well as its lock state
public boolean tryLock()
Acquires the read lock only if the write lock is not held by another thread at the time of invocation. Acquires the read lock if the write lock is not held by another thread and returns immediately with the valuetrue
. Even when this lock has been set to use a fair ordering policy, a call totryLock()
will immediately acquire the read lock if it is available, whether or not other threads are currently waiting for the read 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 usetryLock(0, TimeUnit.SECONDS)
which is almost equivalent (it also detects interruption). If the write lock is held by another thread then this method will return immediately with the valuefalse
.
- Returns:
true
if the read lock was acquired
public boolean tryLock(long timeout, TimeUnit unit) throws InterruptedException
Acquires the read lock if the write lock is not held by another thread within the given waiting time and the current thread has not been interrupted. Acquires the read lock if the write lock is not held by another thread and returns immediately with the valuetrue
. 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 lock. This is in contrast to thetryLock()
method. If you want a timedtryLock
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 write 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 read lock is acquired then the value
- The read lock is acquired by the current thread; or
- Some other thread interrupts the current thread; or
- The specified waiting time elapses.
true
is returned. If the current thread:then
- has its interrupted status set on entry to this method; or
- is interrupted while acquiring the read lock,
InterruptedException
is thrown and the current thread's interrupted status is cleared. If the specified waiting time elapses then the valuefalse
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 read lockunit
- the time unit of the timeout argument
- Returns:
true
if the read lock was acquired