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Préférences
Moteurs de recherche
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JavaTM 2 Platform Std. Ed. v1.5.0
java.util.concurrent.locks
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Method Summary | |
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void |
lock()
Acquires the lock. |
void |
lockInterruptibly()
Acquires the lock unless the current thread is interrupted . |
Condition |
newCondition()
Returns a new Condition instance that is bound to this
Lock instance. |
boolean |
tryLock()
Acquires the lock only if it is free at the time of invocation. |
boolean |
tryLock(long time,
TimeUnit unit)
Acquires the lock if it is free within the given waiting time and the current thread has not been interrupted . |
void |
unlock()
Releases the lock. |
Method Detail |
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void lock()
If the lock is not available then the current thread becomes disabled for thread scheduling purposes and lies dormant until the lock has been acquired.
Implementation Considerations
A Lock implementation may be able to detect erroneous use of the lock, such as an invocation that would cause deadlock, and may throw an (unchecked) exception in such circumstances. The circumstances and the exception type must be documented by that Lock implementation.
void lockInterruptibly() throws InterruptedException
interrupted
.
Acquires the lock if it is available and returns immediately.
If the lock is not available then the current thread becomes disabled for thread scheduling purposes and lies dormant until one of two things happens:
interrupts
the current
thread, and interruption of lock acquisition is supported.
If the current thread:
interrupted
while acquiring
the lock, and interruption of lock acquisition is supported,
InterruptedException
is thrown and the current thread's
interrupted status is cleared.
Implementation Considerations
The ability to interrupt a lock acquisition in some implementations may not be possible, and if possible may be an expensive operation. The programmer should be aware that this may be the case. An implementation should document when this is the case.
An implementation can favor responding to an interrupt over normal method return.
A Lock implementation may be able to detect erroneous use of the lock, such as an invocation that would cause deadlock, and may throw an (unchecked) exception in such circumstances. The circumstances and the exception type must be documented by that Lock implementation.
InterruptedException
- if the current thread is interrupted
while acquiring the lock (and interruption of lock acquisition is
supported).Thread.interrupt()
boolean tryLock()
Acquires the lock if it is available and returns immediately with the value true. If the lock is not available then this method will return immediately with the value false.
A typical usage idiom for this method would be:
Lock lock = ...; if (lock.tryLock()) { try { // manipulate protected state } finally { lock.unlock(); } } else { // perform alternative actions }This usage ensures that the lock is unlocked if it was acquired, and doesn't try to unlock if the lock was not acquired.
boolean tryLock(long time, TimeUnit unit) throws InterruptedException
interrupted
.
If the lock is available this method returns immediately with the value true. If the lock is not available then the current thread becomes disabled for thread scheduling purposes and lies dormant until one of three things happens:
interrupts
the current
thread, and interruption of lock acquisition is supported; or
If the lock is acquired then the value true is returned.
If the current thread:
interrupted
while acquiring
the lock, and interruption of lock acquisition is supported,
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.
Implementation Considerations
The ability to interrupt a lock acquisition in some implementations may not be possible, and if possible may be an expensive operation. The programmer should be aware that this may be the case. An implementation should document when this is the case.
An implementation can favor responding to an interrupt over normal method return, or reporting a timeout.
A Lock implementation may be able to detect erroneous use of the lock, such as an invocation that would cause deadlock, and may throw an (unchecked) exception in such circumstances. The circumstances and the exception type must be documented by that Lock implementation.
time
- the maximum time to wait for the lockunit
- the time unit of the time argument.
InterruptedException
- if the current thread is interrupted
while acquiring the lock (and interruption of lock acquisition is
supported).Thread.interrupt()
void unlock()
Implementation Considerations
A Lock implementation will usually impose restrictions on which thread can release a lock (typically only the holder of the lock can release it) and may throw an (unchecked) exception if the restriction is violated. Any restrictions and the exception type must be documented by that Lock implementation.
Condition newCondition()
Condition
instance that is bound to this
Lock instance.
Before waiting on the condition the lock must be held by the
current thread.
A call to Condition.await()
will atomically release the lock
before waiting and re-acquire the lock before the wait returns.
Implementation Considerations
The exact operation of the Condition
instance depends on the
Lock implementation and must be documented by that
implementation.
Condition
instance for this Lock
instance.
UnsupportedOperationException
- if this Lock
implementation does not support conditions.