| java.lang.Object
 org.drools.util.concurrent.locks.ReentrantLock
| ReentrantLock | | public class ReentrantLock implements Lock,java.io.Serializable(Code) | | This is a stripped down version of jdk1.5 ReentrantLock.
All the condition and wait stuff has been removed
since:
1.5
author:
Doug Lea
author:
Dawid Kurzyniec |
| Inner Class :final static class NonfairSync implements Serializable | |
| Constructor Summary | |
| public | ReentrantLock()
Creates an instance of ReentrantLock. |
| Method Summary | |
| public int | getHoldCount()
Queries the number of holds on this 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.
The hold count information is typically only used for testing and
debugging purposes. | | protected Thread | getOwner()
null if not owned. | | final public int | getQueueLength()
Returns an estimate of the number of threads waiting to
acquire this lock. | | protected Collection | getQueuedThreads()
Returns a collection containing threads that may be waiting to
acquire this lock. | | final public boolean | hasQueuedThread(Thread thread)
Queries whether the given thread is waiting to acquire this
lock. | | final public boolean | hasQueuedThreads()
Queries whether any threads are waiting to acquire this lock. | | public boolean | isHeldByCurrentThread()
Queries if this lock is held by the current thread.
Analogous to the
Thread.holdsLock method for built-in
monitor locks, this method is typically used for debugging and
testing. | | public boolean | isLocked()
Queries if this lock is held by any thread. | | public void | lock()
Acquires the lock. | | public void | lockInterruptibly()
Acquires the lock unless the current thread is
Thread.interrupt interrupted . | | public String | toString()
Returns a string identifying this lock, as well as its lock
state. | | public boolean | tryLock()
Acquires the lock only if it is not held by another thread at the time
of invocation.
Acquires the lock if it is not held by another thread and
returns immediately with the value true, setting the
lock hold count to one. | | public void | unlock()
Attempts to release this lock.
If the current thread is the
holder of this lock then the hold count is decremented. |
| ReentrantLock | | public ReentrantLock()(Code) | | Creates an instance of ReentrantLock.
This is equivalent to using ReentrantLock(false).
|
| getHoldCount | | public int getHoldCount()(Code) | | Queries the number of holds on this 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.
The hold count information is typically only used for testing and
debugging purposes. For example, if a certain section of code should
not be entered with the lock already held then we can assert that
fact:
class X {
ReentrantLock lock = new ReentrantLock();
// ...
public void m() {
assert lock.getHoldCount() == 0;
lock.lock();
try {
// ... method body
} finally {
lock.unlock();
}
}
}
the number of holds on this lock by the current thread,or zero if this lock is not held by the current thread. |
| getOwner | | protected Thread getOwner()(Code) | | null if not owned. When this method is called by a
thread that is not the owner, the return value reflects a
best-effort approximation of current lock status. For example,
the owner may be momentarily null even if there are
threads trying to acquire the lock but have not yet done so.
This method is designed to facilitate construction of
subclasses that provide more extensive lock monitoring
facilities.
the owner, or null if not owned |
| getQueueLength | | final public int getQueueLength()(Code) | | Returns an estimate of the number of threads waiting to
acquire this lock. The value is only an estimate because the number of
threads may change dynamically while this method traverses
internal data structures. This method is designed for use in
monitoring of the system state, not for synchronization
control.
the estimated number of threads waiting for this lock |
| getQueuedThreads | | protected Collection getQueuedThreads()(Code) | | Returns a collection containing threads that may be waiting to
acquire this lock. Because the actual set of threads may change
dynamically while constructing this result, the returned
collection is only a best-effort estimate. The elements of the
returned collection are in no particular order. This method is
designed to facilitate construction of subclasses that provide
more extensive monitoring facilities.
the collection of threads |
| hasQueuedThread | | final public boolean hasQueuedThread(Thread thread)(Code) | | Queries whether the given thread is waiting to acquire this
lock. Note that because cancellations may occur at any time, a
true return does not guarantee that this thread
will ever acquire this lock. This method is designed primarily for use
in monitoring of the system state.
Parameters:
thread - the thread true if the given thread is queued waiting for this lock.
throws:
NullPointerException - if thread is null |
| hasQueuedThreads | | final public boolean hasQueuedThreads()(Code) | | Queries whether any threads are waiting to acquire this lock. Note that
because cancellations may occur at any time, a true
return does not guarantee that any other thread will ever
acquire this lock. This method is designed primarily for use in
monitoring of the system state.
true if there may be other threads waiting to acquirethe lock. |
| isHeldByCurrentThread | | public boolean isHeldByCurrentThread()(Code) | | Queries if this lock is held by the current thread.
Analogous to the
Thread.holdsLock method for built-in
monitor locks, this method is typically used for debugging and
testing. For example, a method that should only be called while
a lock is held can assert that this is the case:
class X {
ReentrantLock lock = new ReentrantLock();
// ...
public void m() {
assert lock.isHeldByCurrentThread();
// ... method body
}
}
It can also be used to ensure that a reentrant lock is used
in a non-reentrant manner, for example:
class X {
ReentrantLock lock = new ReentrantLock();
// ...
public void m() {
assert !lock.isHeldByCurrentThread();
lock.lock();
try {
// ... method body
} finally {
lock.unlock();
}
}
}
true if current thread holds this lock andfalse otherwise. |
| isLocked | | public boolean isLocked()(Code) | | Queries if this lock is held by any thread. This method is
designed for use in monitoring of the system state,
not for synchronization control.
true if any thread holds this lock andfalse otherwise. |
| lock | | public void lock()(Code) | | Acquires the lock.
Acquires the lock if it is not held by another thread and returns
immediately, setting the lock hold count to one.
If the current thread
already holds the 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 lock has been acquired,
at which time the lock hold count is set to one.
|
| lockInterruptibly | | public void lockInterruptibly() throws InterruptedException(Code) | | Acquires the lock unless the current thread is
Thread.interrupt interrupted .
Acquires the lock if it is not held by another thread and returns
immediately, setting the 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 lock is acquired by the current thread; or
- Some other thread
Thread.interrupt interrupts the current
thread.
If the 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
Thread.interrupt interrupted while acquiring
the lock,
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 |
| toString | | public String toString()(Code) | | 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
Thread.getName of the owning thread.
a string identifying this lock, as well as its lock state. |
| tryLock | | public boolean tryLock()(Code) | | Acquires the lock only if it is not held by another thread at the time
of invocation.
Acquires the lock if it is not held by another thread and
returns immediately with the value true, setting the
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 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
ReentrantLock.tryLock(long,TimeUnit) 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 true.
If the lock is held by another thread then this method will return
immediately with the value false.
true if the lock was free and was acquired by thecurrent thread, or the lock was already held by the current thread; andfalse otherwise. |
| unlock | | public void unlock()(Code) | | 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 nothold this lock. |
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