|
Préférences
Moteurs de recherche
|
|||||||||||||||||||||||
JavaTM 2 Platform Std. Ed. v1.6.0
java.util.concurrent.locks
|
Constructor Summary | |
---|---|
protected |
ReentrantReadWriteLock.ReadLock(ReentrantReadWriteLock lock)
Constructor for use by subclasses |
Method Summary | |
---|---|
void |
lock()
Acquires the read lock. |
void |
lockInterruptibly()
Acquires the read lock unless the current thread is interrupted. |
Condition |
newCondition()
Throws UnsupportedOperationException because
ReadLocks do not support conditions. |
String |
toString()
Returns a string identifying this lock, as well as its lock state. |
boolean |
tryLock()
Acquires the read lock only if the write lock is not held by another thread at the time of invocation. |
boolean |
tryLock(long timeout,
TimeUnit unit)
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. |
void |
unlock()
Attempts to release this lock. |
Methods inherited from class java.lang.Object |
---|
clone, equals, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait |
Constructor Detail |
---|
protected ReentrantReadWriteLock.ReadLock(ReentrantReadWriteLock lock)
lock
- the outer lock object
NullPointerException
- if the lock is nullMethod Detail |
---|
public void 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 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:
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.
lockInterruptibly
in interface Lock
InterruptedException
- if the current thread is interruptedpublic boolean tryLock()
Acquires the read lock if the write lock is not held by
another thread and returns immediately with the value
true
. Even when this lock has been set to use a
fair ordering policy, a call to tryLock()
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 use tryLock(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 value
false
.
true
if the read lock was acquiredpublic boolean tryLock(long timeout, TimeUnit unit) throws InterruptedException
Acquires the read lock if the write lock is not held by
another thread and returns immediately with the value
true
. 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 the 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 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 true
is
returned.
If the current thread:
InterruptedException
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.
timeout
- the time to wait for the read lockunit
- the time unit of the timeout argument
true
if the read lock was acquired
InterruptedException
- if the current thread is interrupted
NullPointerException
- if the time unit is nullpublic void unlock()
If the number of readers is now zero then the lock is made available for write lock attempts.
public Condition newCondition()
UnsupportedOperationException
because
ReadLocks
do not support conditions.
newCondition
in interface Lock
Condition
instance for this Lock
instance
UnsupportedOperationException
- alwayspublic String toString()
"Read locks ="
followed by the number of held read locks.