java.util.concurrent.locks
Class ReentrantLock

java.lang.Object sample code for java.lang.Object definition code for java.lang.Object 
  extended by java.util.concurrent.locks.ReentrantLock
All Implemented Interfaces:
Serializable sample code for java.io.Serializable definition code for java.io.Serializable , Lock sample code for java.util.concurrent.locks.Lock definition code for java.util.concurrent.locks.Lock

public class ReentrantLock
extends Object sample code for java.lang.Object definition code for java.lang.Object
implements Lock sample code for java.util.concurrent.locks.Lock definition code for java.util.concurrent.locks.Lock , Serializable sample code for java.io.Serializable definition code for java.io.Serializable

A reentrant mutual exclusion Lock sample code for java.util.concurrent.locks.Lock definition code for java.util.concurrent.locks.Lock with the same basic behavior and semantics as the implicit monitor lock accessed using synchronized methods and statements, but with extended capabilities.

A ReentrantLock is owned by the thread last successfully locking, but not yet unlocking it. A thread invoking lock will return, successfully acquiring the lock, when the lock is not owned by another thread. The method will return immediately if the current thread already owns the lock. This can be checked using methods isHeldByCurrentThread() sample code for java.util.concurrent.locks.ReentrantLock.isHeldByCurrentThread() definition code for java.util.concurrent.locks.ReentrantLock.isHeldByCurrentThread() , and getHoldCount() sample code for java.util.concurrent.locks.ReentrantLock.getHoldCount() definition code for java.util.concurrent.locks.ReentrantLock.getHoldCount() .

The constructor for this class accepts an optional fairness parameter. When set true, under contention, locks favor granting access to the longest-waiting thread. Otherwise this lock does not guarantee any particular access order. Programs using fair locks accessed by many threads may display lower overall throughput (i.e., are slower; often much slower) than those using the default setting, but have smaller variances in times to obtain locks and guarantee lack of starvation. Note however, that fairness of locks does not guarantee fairness of thread scheduling. Thus, one of many threads using a fair lock may obtain it multiple times in succession while other active threads are not progressing and not currently holding the lock. Also note that the untimed tryLock sample code for java.util.concurrent.locks.ReentrantLock.tryLock() definition code for java.util.concurrent.locks.ReentrantLock.tryLock() method does not honor the fairness setting. It will succeed if the lock is available even if other threads are waiting.

It is recommended practice to always immediately follow a call to lock with a try block, most typically in a before/after construction such as:

 class X {
   private final ReentrantLock lock = new ReentrantLock();
   // ...

   public void m() { 
     lock.lock();  // block until condition holds
     try {
       // ... method body
     } finally {
       lock.unlock()
     }
   }
 }
 

In addition to implementing the Lock sample code for java.util.concurrent.locks.Lock definition code for java.util.concurrent.locks.Lock interface, this class defines methods isLocked and getLockQueueLength, as well as some associated protected access methods that may be useful for instrumentation and monitoring.

Serialization of this class behaves in the same way as built-in locks: a deserialized lock is in the unlocked state, regardless of its state when serialized.

This lock supports a maximum of 2147483648 recursive locks by the same thread.

Since:
1.5
See Also:
Serialized Form

Constructor Summary
ReentrantLock sample code for java.util.concurrent.locks.ReentrantLock.ReentrantLock() definition code for java.util.concurrent.locks.ReentrantLock.ReentrantLock() ()
          Creates an instance of ReentrantLock.
ReentrantLock sample code for java.util.concurrent.locks.ReentrantLock.ReentrantLock(boolean) definition code for java.util.concurrent.locks.ReentrantLock.ReentrantLock(boolean) (boolean fair)
          Creates an instance of ReentrantLock with the given fairness policy.
 
Method Summary
 int getHoldCount sample code for java.util.concurrent.locks.ReentrantLock.getHoldCount() definition code for java.util.concurrent.locks.ReentrantLock.getHoldCount() ()
          Queries the number of holds on this lock by the current thread.
protected  Thread sample code for java.lang.Thread definition code for java.lang.Thread getOwner sample code for java.util.concurrent.locks.ReentrantLock.getOwner() definition code for java.util.concurrent.locks.ReentrantLock.getOwner() ()
          Returns the thread that currently owns this lock, or null if not owned.
protected  Collection sample code for java.util.Collection definition code for java.util.Collection <Thread sample code for java.lang.Thread definition code for java.lang.Thread > getQueuedThreads sample code for java.util.concurrent.locks.ReentrantLock.getQueuedThreads() definition code for java.util.concurrent.locks.ReentrantLock.getQueuedThreads() ()
          Returns a collection containing threads that may be waiting to acquire this lock.
 int getQueueLength sample code for java.util.concurrent.locks.ReentrantLock.getQueueLength() definition code for java.util.concurrent.locks.ReentrantLock.getQueueLength() ()
          Returns an estimate of the number of threads waiting to acquire this lock.
protected  Collection sample code for java.util.Collection definition code for java.util.Collection <Thread sample code for java.lang.Thread definition code for java.lang.Thread > getWaitingThreads sample code for java.util.concurrent.locks.ReentrantLock.getWaitingThreads(java.util.concurrent.locks.Condition) definition code for java.util.concurrent.locks.ReentrantLock.getWaitingThreads(java.util.concurrent.locks.Condition) (Condition sample code for java.util.concurrent.locks.Condition definition code for java.util.concurrent.locks.Condition  condition)
          Returns a collection containing those threads that may be waiting on the given condition associated with this lock.
 int getWaitQueueLength sample code for java.util.concurrent.locks.ReentrantLock.getWaitQueueLength(java.util.concurrent.locks.Condition) definition code for java.util.concurrent.locks.ReentrantLock.getWaitQueueLength(java.util.concurrent.locks.Condition) (Condition sample code for java.util.concurrent.locks.Condition definition code for java.util.concurrent.locks.Condition  condition)
          Returns an estimate of the number of threads waiting on the given condition associated with this lock.
 boolean hasQueuedThread sample code for java.util.concurrent.locks.ReentrantLock.hasQueuedThread(java.lang.Thread) definition code for java.util.concurrent.locks.ReentrantLock.hasQueuedThread(java.lang.Thread) (Thread sample code for java.lang.Thread definition code for java.lang.Thread  thread)
          Queries whether the given thread is waiting to acquire this lock.
 boolean hasQueuedThreads sample code for java.util.concurrent.locks.ReentrantLock.hasQueuedThreads() definition code for java.util.concurrent.locks.ReentrantLock.hasQueuedThreads() ()
          Queries whether any threads are waiting to acquire this lock.
 boolean hasWaiters sample code for java.util.concurrent.locks.ReentrantLock.hasWaiters(java.util.concurrent.locks.Condition) definition code for java.util.concurrent.locks.ReentrantLock.hasWaiters(java.util.concurrent.locks.Condition) (Condition sample code for java.util.concurrent.locks.Condition definition code for java.util.concurrent.locks.Condition  condition)
          Queries whether any threads are waiting on the given condition associated with this lock.
 boolean isFair sample code for java.util.concurrent.locks.ReentrantLock.isFair() definition code for java.util.concurrent.locks.ReentrantLock.isFair() ()
          Returns true if this lock has fairness set true.
 boolean isHeldByCurrentThread sample code for java.util.concurrent.locks.ReentrantLock.isHeldByCurrentThread() definition code for java.util.concurrent.locks.ReentrantLock.isHeldByCurrentThread() ()
          Queries if this lock is held by the current thread.
 boolean isLocked sample code for java.util.concurrent.locks.ReentrantLock.isLocked() definition code for java.util.concurrent.locks.ReentrantLock.isLocked() ()
          Queries if this lock is held by any thread.
 void lock sample code for java.util.concurrent.locks.ReentrantLock.lock() definition code for java.util.concurrent.locks.ReentrantLock.lock() ()
          Acquires the lock.
 void lockInterruptibly sample code for java.util.concurrent.locks.ReentrantLock.lockInterruptibly() definition code for java.util.concurrent.locks.ReentrantLock.lockInterruptibly() ()
          Acquires the lock unless the current thread is interrupted sample code for java.lang.Thread.interrupt() definition code for java.lang.Thread.interrupt() .
 Condition sample code for java.util.concurrent.locks.Condition definition code for java.util.concurrent.locks.Condition newCondition sample code for java.util.concurrent.locks.ReentrantLock.newCondition() definition code for java.util.concurrent.locks.ReentrantLock.newCondition() ()
          Returns a Condition sample code for java.util.concurrent.locks.Condition definition code for java.util.concurrent.locks.Condition instance for use with this Lock sample code for java.util.concurrent.locks.Lock definition code for java.util.concurrent.locks.Lock instance.
 String sample code for java.lang.String definition code for java.lang.String toString sample code for java.util.concurrent.locks.ReentrantLock.toString() definition code for java.util.concurrent.locks.ReentrantLock.toString() ()
          Returns a string identifying this lock, as well as its lock state.
 boolean tryLock sample code for java.util.concurrent.locks.ReentrantLock.tryLock() definition code for java.util.concurrent.locks.ReentrantLock.tryLock() ()
          Acquires the lock only if it is not held by another thread at the time of invocation.
 boolean tryLock sample code for java.util.concurrent.locks.ReentrantLock.tryLock(long, java.util.concurrent.TimeUnit) definition code for java.util.concurrent.locks.ReentrantLock.tryLock(long, java.util.concurrent.TimeUnit) (long timeout, TimeUnit sample code for java.util.concurrent.TimeUnit definition code for java.util.concurrent.TimeUnit  unit)
          Acquires the lock if it is not held by another thread within the given waiting time and the current thread has not been interrupted sample code for java.lang.Thread.interrupt() definition code for java.lang.Thread.interrupt() .
 void unlock sample code for java.util.concurrent.locks.ReentrantLock.unlock() definition code for java.util.concurrent.locks.ReentrantLock.unlock() ()
          Attempts to release this lock.
 
Methods inherited from class java.lang.Object sample code for java.lang.Object definition code for java.lang.Object
clone sample code for java.lang.Object.clone() definition code for java.lang.Object.clone() , equals sample code for java.lang.Object.equals(java.lang.Object) definition code for java.lang.Object.equals(java.lang.Object) , finalize sample code for java.lang.Object.finalize() definition code for java.lang.Object.finalize() , getClass sample code for java.lang.Object.getClass() definition code for java.lang.Object.getClass() , hashCode sample code for java.lang.Object.hashCode() definition code for java.lang.Object.hashCode() , notify sample code for java.lang.Object.notify() definition code for java.lang.Object.notify() , notifyAll sample code for java.lang.Object.notifyAll() definition code for java.lang.Object.notifyAll() , wait sample code for java.lang.Object.wait() definition code for java.lang.Object.wait() , wait sample code for java.lang.Object.wait(long) definition code for java.lang.Object.wait(long) , wait sample code for java.lang.Object.wait(long, int) definition code for java.lang.Object.wait(long, int)
 

Constructor Detail

ReentrantLock sample code for java.util.concurrent.locks.ReentrantLock() definition code for java.util.concurrent.locks.ReentrantLock()

public ReentrantLock()
Creates an instance of ReentrantLock. This is equivalent to using ReentrantLock(false).


ReentrantLock sample code for java.util.concurrent.locks.ReentrantLock(boolean) definition code for java.util.concurrent.locks.ReentrantLock(boolean)

public ReentrantLock(boolean fair)
Creates an instance of ReentrantLock with the given fairness policy.

Parameters:
fair - true if this lock will be fair; else false
Method Detail

lock sample code for java.util.concurrent.locks.ReentrantLock.lock() definition code for java.util.concurrent.locks.ReentrantLock.lock()

public void lock()
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.

Specified by:
lock sample code for java.util.concurrent.locks.Lock.lock() definition code for java.util.concurrent.locks.Lock.lock() in interface Lock sample code for java.util.concurrent.locks.Lock definition code for java.util.concurrent.locks.Lock

lockInterruptibly sample code for java.util.concurrent.locks.ReentrantLock.lockInterruptibly() definition code for java.util.concurrent.locks.ReentrantLock.lockInterruptibly()

public void lockInterruptibly()
                       throws InterruptedException sample code for java.lang.InterruptedException definition code for java.lang.InterruptedException 
Acquires the lock unless the current thread is interrupted sample code for java.lang.Thread.interrupt() definition code for java.lang.Thread.interrupt() .

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:

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

If the current thread:

then InterruptedException sample code for java.lang.InterruptedException definition code for java.lang.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 sample code for java.util.concurrent.locks.Lock.lockInterruptibly() definition code for java.util.concurrent.locks.Lock.lockInterruptibly() in interface Lock sample code for java.util.concurrent.locks.Lock definition code for java.util.concurrent.locks.Lock
Throws:
InterruptedException sample code for java.lang.InterruptedException definition code for java.lang.InterruptedException - if the current thread is interrupted
See Also:
Thread.interrupt() sample code for java.lang.Thread.interrupt() definition code for java.lang.Thread.interrupt()

tryLock sample code for java.util.concurrent.locks.ReentrantLock.tryLock() definition code for java.util.concurrent.locks.ReentrantLock.tryLock()

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. 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 tryLock(0, TimeUnit.SECONDS) sample code for java.util.concurrent.locks.ReentrantLock.tryLock(long, java.util.concurrent.TimeUnit) definition code for java.util.concurrent.locks.ReentrantLock.tryLock(long, java.util.concurrent.TimeUnit) 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.

Specified by:
tryLock sample code for java.util.concurrent.locks.Lock.tryLock() definition code for java.util.concurrent.locks.Lock.tryLock() in interface Lock sample code for java.util.concurrent.locks.Lock definition code for java.util.concurrent.locks.Lock
Returns:
true if the lock was free and was acquired by the current thread, or the lock was already held by the current thread; and false otherwise.

tryLock sample code for java.util.concurrent.locks.ReentrantLock.tryLock(long, java.util.concurrent.TimeUnit) definition code for java.util.concurrent.locks.ReentrantLock.tryLock(long, java.util.concurrent.TimeUnit)

public boolean tryLock(long timeout,
                       TimeUnit sample code for java.util.concurrent.TimeUnit definition code for java.util.concurrent.TimeUnit  unit)
                throws InterruptedException sample code for java.lang.InterruptedException definition code for java.lang.InterruptedException 
Acquires the lock if it is not held by another thread within the given waiting time and the current thread has not been interrupted sample code for java.lang.Thread.interrupt() definition code for java.lang.Thread.interrupt() .

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. 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() sample code for java.util.concurrent.locks.ReentrantLock.tryLock() definition code for java.util.concurrent.locks.ReentrantLock.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 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 the current thread becomes disabled for thread scheduling purposes and lies dormant until one of three things happens:

If the lock is acquired then the value true is returned and the lock hold count is set to one.

If the current thread:

then InterruptedException sample code for java.lang.InterruptedException definition code for java.lang.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.

Specified by:
tryLock sample code for java.util.concurrent.locks.Lock.tryLock(long, java.util.concurrent.TimeUnit) definition code for java.util.concurrent.locks.Lock.tryLock(long, java.util.concurrent.TimeUnit) in interface Lock sample code for java.util.concurrent.locks.Lock definition code for java.util.concurrent.locks.Lock
Parameters:
timeout - the time to wait for the lock
unit - the time unit of the timeout argument
Returns:
true if the lock was free and was acquired by the current thread, or the lock was already held by the current thread; and false if the waiting time elapsed before the lock could be acquired.
Throws:
InterruptedException sample code for java.lang.InterruptedException definition code for java.lang.InterruptedException - if the current thread is interrupted
NullPointerException sample code for java.lang.NullPointerException definition code for java.lang.NullPointerException - if unit is null
See Also:
Thread.interrupt() sample code for java.lang.Thread.interrupt() definition code for java.lang.Thread.interrupt()

unlock sample code for java.util.concurrent.locks.ReentrantLock.unlock() definition code for java.util.concurrent.locks.ReentrantLock.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 sample code for java.lang.IllegalMonitorStateException definition code for java.lang.IllegalMonitorStateException is thrown.

Specified by:
unlock sample code for java.util.concurrent.locks.Lock.unlock() definition code for java.util.concurrent.locks.Lock.unlock() in interface Lock sample code for java.util.concurrent.locks.Lock definition code for java.util.concurrent.locks.Lock
Throws:
IllegalMonitorStateException sample code for java.lang.IllegalMonitorStateException definition code for java.lang.IllegalMonitorStateException - if the current thread does not hold this lock.

newCondition sample code for java.util.concurrent.locks.ReentrantLock.newCondition() definition code for java.util.concurrent.locks.ReentrantLock.newCondition()

public Condition sample code for java.util.concurrent.locks.Condition definition code for java.util.concurrent.locks.Condition  newCondition()
Returns a Condition sample code for java.util.concurrent.locks.Condition definition code for java.util.concurrent.locks.Condition instance for use with this Lock sample code for java.util.concurrent.locks.Lock definition code for java.util.concurrent.locks.Lock instance.

The returned Condition sample code for java.util.concurrent.locks.Condition definition code for java.util.concurrent.locks.Condition instance supports the same usages as do the Object sample code for java.lang.Object definition code for java.lang.Object monitor methods (wait sample code for java.lang.Object.wait() definition code for java.lang.Object.wait() , notify sample code for java.lang.Object.notify() definition code for java.lang.Object.notify() , and notifyAll sample code for java.lang.Object.notifyAll() definition code for java.lang.Object.notifyAll() ) when used with the built-in monitor lock.

Specified by:
newCondition sample code for java.util.concurrent.locks.Lock.newCondition() definition code for java.util.concurrent.locks.Lock.newCondition() in interface Lock sample code for java.util.concurrent.locks.Lock definition code for java.util.concurrent.locks.Lock
Returns:
the Condition object

getHoldCount sample code for java.util.concurrent.locks.ReentrantLock.getHoldCount() definition code for java.util.concurrent.locks.ReentrantLock.getHoldCount()

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. 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();
     }
   }
 }
 

Returns:
the number of holds on this lock by the current thread, or zero if this lock is not held by the current thread.

isHeldByCurrentThread sample code for java.util.concurrent.locks.ReentrantLock.isHeldByCurrentThread() definition code for java.util.concurrent.locks.ReentrantLock.isHeldByCurrentThread()

public boolean isHeldByCurrentThread()
Queries if this lock is held by the current thread.

Analogous to the Thread.holdsLock(java.lang.Object) sample code for java.lang.Thread.holdsLock(java.lang.Object) definition code for java.lang.Thread.holdsLock(java.lang.Object) 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();
       }
   }
 }
 

Returns:
true if current thread holds this lock and false otherwise.

isLocked sample code for java.util.concurrent.locks.ReentrantLock.isLocked() definition code for java.util.concurrent.locks.ReentrantLock.isLocked()

public boolean isLocked()
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.

Returns:
true if any thread holds this lock and false otherwise.

isFair sample code for java.util.concurrent.locks.ReentrantLock.isFair() definition code for java.util.concurrent.locks.ReentrantLock.isFair()

public final boolean isFair()
Returns true if this lock has fairness set true.

Returns:
true if this lock has fairness set true.

getOwner sample code for java.util.concurrent.locks.ReentrantLock.getOwner() definition code for java.util.concurrent.locks.ReentrantLock.getOwner()

protected Thread sample code for java.lang.Thread definition code for java.lang.Thread  getOwner()
Returns the thread that currently owns this lock, or null if not owned. Note that 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.

Returns:
the owner, or null if not owned.

hasQueuedThreads sample code for java.util.concurrent.locks.ReentrantLock.hasQueuedThreads() definition code for java.util.concurrent.locks.ReentrantLock.hasQueuedThreads()

public final boolean hasQueuedThreads()
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.

Returns:
true if there may be other threads waiting to acquire the lock.

hasQueuedThread sample code for java.util.concurrent.locks.ReentrantLock.hasQueuedThread(java.lang.Thread) definition code for java.util.concurrent.locks.ReentrantLock.hasQueuedThread(java.lang.Thread)

public final boolean hasQueuedThread(Thread sample code for java.lang.Thread definition code for java.lang.Thread  thread)
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
Returns:
true if the given thread is queued waiting for this lock.
Throws:
NullPointerException sample code for java.lang.NullPointerException definition code for java.lang.NullPointerException - if thread is null

getQueueLength sample code for java.util.concurrent.locks.ReentrantLock.getQueueLength() definition code for java.util.concurrent.locks.ReentrantLock.getQueueLength()

public final int getQueueLength()
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.

Returns:
the estimated number of threads waiting for this lock

getQueuedThreads sample code for java.util.concurrent.locks.ReentrantLock.getQueuedThreads() definition code for java.util.concurrent.locks.ReentrantLock.getQueuedThreads()

protected Collection sample code for java.util.Collection definition code for java.util.Collection <Thread sample code for java.lang.Thread definition code for java.lang.Thread > getQueuedThreads()
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.

Returns:
the collection of threads

hasWaiters sample code for java.util.concurrent.locks.ReentrantLock.hasWaiters(java.util.concurrent.locks.Condition) definition code for java.util.concurrent.locks.ReentrantLock.hasWaiters(java.util.concurrent.locks.Condition)

public boolean hasWaiters(Condition sample code for java.util.concurrent.locks.Condition definition code for java.util.concurrent.locks.Condition  condition)
Queries whether any threads are waiting on the given condition associated with this lock. Note that because timeouts and interrupts may occur at any time, a true return does not guarantee that a future signal will awaken any threads. This method is designed primarily for use in monitoring of the system state.

Parameters:
condition - the condition
Returns:
true if there are any waiting threads.
Throws:
IllegalMonitorStateException sample code for java.lang.IllegalMonitorStateException definition code for java.lang.IllegalMonitorStateException - if this lock is not held
IllegalArgumentException sample code for java.lang.IllegalArgumentException definition code for java.lang.IllegalArgumentException - if the given condition is not associated with this lock
NullPointerException sample code for java.lang.NullPointerException definition code for java.lang.NullPointerException - if condition null

getWaitQueueLength sample code for java.util.concurrent.locks.ReentrantLock.getWaitQueueLength(java.util.concurrent.locks.Condition) definition code for java.util.concurrent.locks.ReentrantLock.getWaitQueueLength(java.util.concurrent.locks.Condition)

public int getWaitQueueLength(Condition sample code for java.util.concurrent.locks.Condition definition code for java.util.concurrent.locks.Condition  condition)
Returns an estimate of the number of threads waiting on the given condition associated with this lock. Note that because timeouts and interrupts may occur at any time, the estimate serves only as an upper bound on the actual number of waiters. This method is designed for use in monitoring of the system state, not for synchronization control.

Parameters:
condition - the condition
Returns:
the estimated number of waiting threads.
Throws:
IllegalMonitorStateException sample code for java.lang.IllegalMonitorStateException definition code for java.lang.IllegalMonitorStateException - if this lock is not held
IllegalArgumentException sample code for java.lang.IllegalArgumentException definition code for java.lang.IllegalArgumentException - if the given condition is not associated with this lock
NullPointerException sample code for java.lang.NullPointerException definition code for java.lang.NullPointerException - if condition null

getWaitingThreads sample code for java.util.concurrent.locks.ReentrantLock.getWaitingThreads(java.util.concurrent.locks.Condition) definition code for java.util.concurrent.locks.ReentrantLock.getWaitingThreads(java.util.concurrent.locks.Condition)

protected Collection sample code for java.util.Collection definition code for java.util.Collection <Thread sample code for java.lang.Thread definition code for java.lang.Thread > getWaitingThreads(Condition sample code for java.util.concurrent.locks.Condition definition code for java.util.concurrent.locks.Condition  condition)
Returns a collection containing those threads that may be waiting on the given condition associated with 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 condition monitoring facilities.

Parameters:
condition - the condition
Returns:
the collection of threads
Throws:
IllegalMonitorStateException sample code for java.lang.IllegalMonitorStateException definition code for java.lang.IllegalMonitorStateException - if this lock is not held
IllegalArgumentException sample code for java.lang.IllegalArgumentException definition code for java.lang.IllegalArgumentException - if the given condition is not associated with this lock
NullPointerException sample code for java.lang.NullPointerException definition code for java.lang.NullPointerException - if condition null

toString sample code for java.util.concurrent.locks.ReentrantLock.toString() definition code for java.util.concurrent.locks.ReentrantLock.toString()

public String sample code for java.lang.String definition code for java.lang.String  toString()
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() sample code for java.lang.Thread.getName() definition code for java.lang.Thread.getName() of the owning thread.

Overrides:
toString sample code for java.lang.Object.toString() definition code for java.lang.Object.toString() in class Object sample code for java.lang.Object definition code for java.lang.Object
Returns:
a string identifying this lock, as well as its lock state.