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*java.util.concurrent.locks.AbstractQueuedSynchronizer* *AbstractQueuedSynchronizer* 

public abstract class AbstractQueuedSynchronizer
  extends    |java.lang.Object|
  implements |java.io.Serializable|

|java.util.concurrent.locks.AbstractQueuedSynchronizer_Description|
|java.util.concurrent.locks.AbstractQueuedSynchronizer_Fields|
|java.util.concurrent.locks.AbstractQueuedSynchronizer_Constructors|
|java.util.concurrent.locks.AbstractQueuedSynchronizer_Methods|

================================================================================

*java.util.concurrent.locks.AbstractQueuedSynchronizer_Constructors*
|java.util.concurrent.locks.AbstractQueuedSynchronizer()|Creates a new Abstract

*java.util.concurrent.locks.AbstractQueuedSynchronizer_Methods*
|java.util.concurrent.locks.AbstractQueuedSynchronizer.acquire(int)|Acquires in
|java.util.concurrent.locks.AbstractQueuedSynchronizer.acquireInterruptibly(int)|
|java.util.concurrent.locks.AbstractQueuedSynchronizer.acquireShared(int)|Acqui
|java.util.concurrent.locks.AbstractQueuedSynchronizer.acquireSharedInterruptibly(int)|
|java.util.concurrent.locks.AbstractQueuedSynchronizer.compareAndSetState(int,int)|
|java.util.concurrent.locks.AbstractQueuedSynchronizer.getExclusiveQueuedThreads()|
|java.util.concurrent.locks.AbstractQueuedSynchronizer.getFirstQueuedThread()|R
|java.util.concurrent.locks.AbstractQueuedSynchronizer.getQueuedThreads()|Retur
|java.util.concurrent.locks.AbstractQueuedSynchronizer.getQueueLength()|Returns
|java.util.concurrent.locks.AbstractQueuedSynchronizer.getSharedQueuedThreads()|
|java.util.concurrent.locks.AbstractQueuedSynchronizer.getState()|Returns the c
|java.util.concurrent.locks.AbstractQueuedSynchronizer.getWaitingThreads(AbstractQueuedSynchronizer.ConditionObject)|
|java.util.concurrent.locks.AbstractQueuedSynchronizer.getWaitQueueLength(AbstractQueuedSynchronizer.ConditionObject)|
|java.util.concurrent.locks.AbstractQueuedSynchronizer.hasContended()|Queries w
|java.util.concurrent.locks.AbstractQueuedSynchronizer.hasQueuedThreads()|Queri
|java.util.concurrent.locks.AbstractQueuedSynchronizer.hasWaiters(AbstractQueuedSynchronizer.ConditionObject)|
|java.util.concurrent.locks.AbstractQueuedSynchronizer.isHeldExclusively()|Retu
|java.util.concurrent.locks.AbstractQueuedSynchronizer.isQueued(Thread)|Returns
|java.util.concurrent.locks.AbstractQueuedSynchronizer.owns(AbstractQueuedSynchronizer.ConditionObject)|
|java.util.concurrent.locks.AbstractQueuedSynchronizer.release(int)|Releases in
|java.util.concurrent.locks.AbstractQueuedSynchronizer.releaseShared(int)|Relea
|java.util.concurrent.locks.AbstractQueuedSynchronizer.setState(int)|Sets the v
|java.util.concurrent.locks.AbstractQueuedSynchronizer.toString()|Returns a str
|java.util.concurrent.locks.AbstractQueuedSynchronizer.tryAcquire(int)|Attempts
|java.util.concurrent.locks.AbstractQueuedSynchronizer.tryAcquireNanos(int,long)|
|java.util.concurrent.locks.AbstractQueuedSynchronizer.tryAcquireShared(int)|At
|java.util.concurrent.locks.AbstractQueuedSynchronizer.tryAcquireSharedNanos(int,long)|
|java.util.concurrent.locks.AbstractQueuedSynchronizer.tryRelease(int)|Attempts
|java.util.concurrent.locks.AbstractQueuedSynchronizer.tryReleaseShared(int)|At

*java.util.concurrent.locks.AbstractQueuedSynchronizer_Description*

Provides a framework for implementing blocking locks and related synchronizers 
(semaphores, events, etc) that rely on first-in-first-out (FIFO) wait queues. 
This class is designed to be a useful basis for most kinds of synchronizers 
that rely on a single atomic int value to represent state. Subclasses must 
define the protected methods that change this state, and which define what that 
state means in terms of this object being acquired or released. Given these, 
the other methods in this class carry out all queuing and blocking mechanics. 
Subclasses can maintain other state fields, but only the atomically updated int 
value manipulated using methods 
(|java.util.concurrent.locks.AbstractQueuedSynchronizer|) , 
(|java.util.concurrent.locks.AbstractQueuedSynchronizer|) and 
(|java.util.concurrent.locks.AbstractQueuedSynchronizer|) is tracked with 
respect to synchronization. 

Subclasses should be defined as non-public internal helper classes that are 
used to implement the synchronization properties of their enclosing class. 
Class AbstractQueuedSynchronizer does not implement any synchronization 
interface. Instead it defines methods such as 
(|java.util.concurrent.locks.AbstractQueuedSynchronizer|) that can be invoked 
as appropriate by concrete locks and related synchronizers to implement their 
public methods. 

This class supports either or both a default exclusive mode and a shared mode. 
When acquired in exclusive mode, attempted acquires by other threads cannot 
succeed. Shared mode acquires by multiple threads may (but need not) succeed. 
This class does not understand these differences except in the mechanical sense 
that when a shared mode acquire succeeds, the next waiting thread (if one 
exists) must also determine whether it can acquire as well. Threads waiting in 
the different modes share the same FIFO queue. Usually, implementation 
subclasses support only one of these modes, but both can come into play for 
example in a (|java.util.concurrent.locks.ReadWriteLock|) . Subclasses that 
support only exclusive or only shared modes need not define the methods 
supporting the unused mode. 

This class defines a nested 
(|java.util.concurrent.locks.AbstractQueuedSynchronizer.ConditionObject|) class 
that can be used as a (|java.util.concurrent.locks.Condition|) implementation 
by subclasses supporting exclusive mode for which method 
(|java.util.concurrent.locks.AbstractQueuedSynchronizer|) reports whether 
synchronization is exclusively held with respect to the current thread, method 
(|java.util.concurrent.locks.AbstractQueuedSynchronizer|) invoked with the 
current (|java.util.concurrent.locks.AbstractQueuedSynchronizer|) value fully 
releases this object, and 
(|java.util.concurrent.locks.AbstractQueuedSynchronizer|) , given this saved 
state value, eventually restores this object to its previous acquired state. No 
AbstractQueuedSynchronizer method otherwise creates such a condition, so if 
this constraint cannot be met, do not use it. The behavior of 
(|java.util.concurrent.locks.AbstractQueuedSynchronizer.ConditionObject|) 
depends of course on the semantics of its synchronizer implementation. 

This class provides inspection, instrumentation, and monitoring methods for the 
internal queue, as well as similar methods for condition objects. These can be 
exported as desired into classes using an AbstractQueuedSynchronizer for their 
synchronization mechanics. 

Serialization of this class stores only the underlying atomic integer 
maintaining state, so deserialized objects have empty thread queues. Typical 
subclasses requiring serializability will define a readObject method that 
restores this to a known initial state upon deserialization. 

Usage 

To use this class as the basis of a synchronizer, redefine the following 
methods, as applicable, by inspecting and/or modifying the synchronization 
state using (|java.util.concurrent.locks.AbstractQueuedSynchronizer|) , 
(|java.util.concurrent.locks.AbstractQueuedSynchronizer|) and/or 
(|java.util.concurrent.locks.AbstractQueuedSynchronizer|) : 

(|java.util.concurrent.locks.AbstractQueuedSynchronizer|) 
(|java.util.concurrent.locks.AbstractQueuedSynchronizer|) 
(|java.util.concurrent.locks.AbstractQueuedSynchronizer|) 
(|java.util.concurrent.locks.AbstractQueuedSynchronizer|) 
(|java.util.concurrent.locks.AbstractQueuedSynchronizer|) 

Each of these methods by default throws 
(|java.lang.UnsupportedOperationException|) . Implementations of these methods 
must be internally thread-safe, and should in general be short and not block. 
Defining these methods is the only supported means of using this class. All 
other methods are declared final because they cannot be independently varied. 

Even though this class is based on an internal FIFO queue, it does not 
automatically enforce FIFO acquisition policies. The core of exclusive 
synchronization takes the form: 



Acquire: while (!tryAcquire(arg)) { enqueue thread if it is not already queued; 
possibly block current thread; } 

Release: if (tryRelease(arg)) unblock the first queued thread; 

(Shared mode is similar but may involve cascading signals.) 

Because checks in acquire are invoked before enqueuing, a newly acquiring 
thread may barge ahead of others that are blocked and queued. However, you can, 
if desired, define tryAcquire and/or tryAcquireShared to disable barging by 
internally invoking one or more of the inspection methods. In particular, a 
strict FIFO lock can define tryAcquire to immediately return false if 
(|java.util.concurrent.locks.AbstractQueuedSynchronizer|) does not return the 
current thread. A normally preferable non-strict fair version can immediately 
return false only if (|java.util.concurrent.locks.AbstractQueuedSynchronizer|) 
returns true and getFirstQueuedThread is not the current thread; or 
equivalently, that getFirstQueuedThread is both non-null and not the current 
thread. Further variations are possible. 

Throughput and scalability are generally highest for the default barging (also 
known as greedy, renouncement, and convoy-avoidance) strategy. While this is 
not guaranteed to be fair or starvation-free, earlier queued threads are 
allowed to recontend before later queued threads, and each recontention has an 
unbiased chance to succeed against incoming threads. Also, while acquires do 
not spin in the usual sense, they may perform multiple invocations of 
tryAcquire interspersed with other computations before blocking. This gives 
most of the benefits of spins when exclusive synchronization is only briefly 
held, without most of the liabilities when it isn't. If so desired, you can 
augment this by preceding calls to acquire methods with "fast-path" checks, 
possibly prechecking (|java.util.concurrent.locks.AbstractQueuedSynchronizer|) 
and/or (|java.util.concurrent.locks.AbstractQueuedSynchronizer|) to only do so 
if the synchronizer is likely not to be contended. 

This class provides an efficient and scalable basis for synchronization in part 
by specializing its range of use to synchronizers that can rely on int state, 
acquire, and release parameters, and an internal FIFO wait queue. When this 
does not suffice, you can build synchronizers from a lower level using 
atomic(|java.util.concurrent.atomic|) classes, your own custom 
(|java.util.Queue|) classes, and (|java.util.concurrent.locks.LockSupport|) 
blocking support. 

Usage Examples 

Here is a non-reentrant mutual exclusion lock class that uses the value zero to 
represent the unlocked state, and one to represent the locked state. It also 
supports conditions and exposes one of the instrumentation methods: 



class Mutex implements Lock, java.io.Serializable { 

// Our internal helper class private static class Sync extends 
AbstractQueuedSynchronizer { // Report whether in locked state protected 
boolean isHeldExclusively() { return getState() == 1; } 

// Acquire the lock if state is zero public boolean tryAcquire(int acquires) { 
assert acquires == 1; // Otherwise unused return compareAndSetState(0, 1); } 

// Release the lock by setting state to zero protected boolean tryRelease(int 
releases) { assert releases == 1; // Otherwise unused if (getState() == 0) 
throw new IllegalMonitorStateException(); setState(0); return true; } 

// Provide a Condition Condition newCondition() { return new ConditionObject(); 
} 

// Deserialize properly private void readObject(ObjectInputStream s) throws 
IOException, ClassNotFoundException { s.defaultReadObject(); setState(0); // 
reset to unlocked state } } 

// The sync object does all the hard work. We just forward to it. private final 
Sync sync = new Sync(); 

public void lock() { sync.acquire(1); } public boolean tryLock() { return 
sync.tryAcquire(1); } public void unlock() { sync.release(1); } public 
Condition newCondition() { return sync.newCondition(); } public boolean 
isLocked() { return sync.isHeldExclusively(); } public boolean 
hasQueuedThreads() { return sync.hasQueuedThreads(); } public void 
lockInterruptibly() throws InterruptedException { sync.acquireInterruptibly(1); 
} public boolean tryLock(long timeout, TimeUnit unit) throws 
InterruptedException { return sync.tryAcquireNanos(1, unit.toNanos(timeout)); } 
} 

Here is a latch class that is like a (|java.util.concurrent.CountDownLatch|) 
except that it only requires a single signal to fire. Because a latch is 
non-exclusive, it uses the shared acquire and release methods. 



class BooleanLatch { 

private static class Sync extends AbstractQueuedSynchronizer { boolean 
isSignalled() { return getState() != 0; } 

protected int tryAcquireShared(int ignore) { return isSignalled()? 1 : -1; } 

protected boolean tryReleaseShared(int ignore) { setState(1); return true; } } 

private final Sync sync = new Sync(); public boolean isSignalled() { return 
sync.isSignalled(); } public void signal() { sync.releaseShared(1); } public 
void await() throws InterruptedException { sync.acquireSharedInterruptibly(1); 
} } 




*java.util.concurrent.locks.AbstractQueuedSynchronizer()*

protected AbstractQueuedSynchronizer()

Creates a new AbstractQueuedSynchronizer instance with initial synchronization 
state of zero. 


*java.util.concurrent.locks.AbstractQueuedSynchronizer.acquire(int)*

public final void acquire(int arg)

Acquires in exclusive mode, ignoring interrupts. Implemented by invoking at 
least once (|java.util.concurrent.locks.AbstractQueuedSynchronizer|) , 
returning on success. Otherwise the thread is queued, possibly repeatedly 
blocking and unblocking, invoking 
(|java.util.concurrent.locks.AbstractQueuedSynchronizer|) until success. This 
method can be used to implement method (|java.util.concurrent.locks.Lock|) 

    arg - the acquire argument. This value is conveyed to {@link #tryAcquire} but is 
       otherwise uninterpreted and can represent anything you like. 

*java.util.concurrent.locks.AbstractQueuedSynchronizer.acquireInterruptibly(int)*

public final void acquireInterruptibly(int arg)
  throws |java.lang.InterruptedException|
         
Acquires in exclusive mode, aborting if interrupted. Implemented by first 
checking interrupt status, then invoking at least once 
(|java.util.concurrent.locks.AbstractQueuedSynchronizer|) , returning on 
success. Otherwise the thread is queued, possibly repeatedly blocking and 
unblocking, invoking (|java.util.concurrent.locks.AbstractQueuedSynchronizer|) 
until success or the thread is interrupted. This method can be used to 
implement method (|java.util.concurrent.locks.Lock|) 

    arg - the acquire argument. This value is conveyed to {@link #tryAcquire} but is 
       otherwise uninterpreted and can represent anything you like. 

*java.util.concurrent.locks.AbstractQueuedSynchronizer.acquireShared(int)*

public final void acquireShared(int arg)

Acquires in shared mode, ignoring interrupts. Implemented by first invoking at 
least once (|java.util.concurrent.locks.AbstractQueuedSynchronizer|) , 
returning on success. Otherwise the thread is queued, possibly repeatedly 
blocking and unblocking, invoking 
(|java.util.concurrent.locks.AbstractQueuedSynchronizer|) until success. 

    arg - the acquire argument. This value is conveyed to {@link #tryAcquireShared} but 
       is otherwise uninterpreted and can represent anything you like. 

*java.util.concurrent.locks.AbstractQueuedSynchronizer.acquireSharedInterruptibly(int)*

public final void acquireSharedInterruptibly(int arg)
  throws |java.lang.InterruptedException|
         
Acquires in shared mode, aborting if interrupted. Implemented by first checking 
interrupt status, then invoking at least once 
(|java.util.concurrent.locks.AbstractQueuedSynchronizer|) , returning on 
success. Otherwise the thread is queued, possibly repeatedly blocking and 
unblocking, invoking (|java.util.concurrent.locks.AbstractQueuedSynchronizer|) 
until success or the thread is interrupted. 

    arg - the acquire argument. This value is conveyed to {@link #tryAcquireShared} but 
       is otherwise uninterpreted and can represent anything you like. 

*java.util.concurrent.locks.AbstractQueuedSynchronizer.compareAndSetState(int,int)*

protected final boolean compareAndSetState(
  int expect,
  int update)

Atomically sets synchronization state to the given updated value if the current 
state value equals the expected value. This operation has memory semantics of a 
volatile read and write. 

    expect - the expected value 
    update - the new value 

    Returns: true if successful. False return indicates that the actual value was not equal 
             to the expected value. 
*java.util.concurrent.locks.AbstractQueuedSynchronizer.getExclusiveQueuedThreads()*

public final |java.util.Collection| getExclusiveQueuedThreads()

Returns a collection containing threads that may be waiting to acquire in 
exclusive mode. This has the same properties as 
(|java.util.concurrent.locks.AbstractQueuedSynchronizer|) except that it only 
returns those threads waiting due to an exclusive acquire. 


    Returns: the collection of threads 
*java.util.concurrent.locks.AbstractQueuedSynchronizer.getFirstQueuedThread()*

public final |java.lang.Thread| getFirstQueuedThread()

Returns the first (longest-waiting) thread in the queue, or null if no threads 
are currently queued. 

In this implementation, this operation normally returns in constant time, but 
may iterate upon contention if other threads are concurrently modifying the 
queue. 


    Returns: the first (longest-waiting) thread in the queue, or null if no threads are 
             currently queued. 
*java.util.concurrent.locks.AbstractQueuedSynchronizer.getQueuedThreads()*

public final |java.util.Collection| getQueuedThreads()

Returns a collection containing threads that may be waiting to acquire. 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 
*java.util.concurrent.locks.AbstractQueuedSynchronizer.getQueueLength()*

public final int getQueueLength()

Returns an estimate of the number of threads waiting to acquire. 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 system state, not for synchronization control. 


    Returns: the estimated number of threads waiting for this lock 
*java.util.concurrent.locks.AbstractQueuedSynchronizer.getSharedQueuedThreads()*

public final |java.util.Collection| getSharedQueuedThreads()

Returns a collection containing threads that may be waiting to acquire in 
shared mode. This has the same properties as 
(|java.util.concurrent.locks.AbstractQueuedSynchronizer|) except that it only 
returns those threads waiting due to a shared acquire. 


    Returns: the collection of threads 
*java.util.concurrent.locks.AbstractQueuedSynchronizer.getState()*

protected final int getState()

Returns the current value of synchronization state. This operation has memory 
semantics of a volatile read. 


    Returns: current state value 
*java.util.concurrent.locks.AbstractQueuedSynchronizer.getWaitingThreads(AbstractQueuedSynchronizer.ConditionObject)*

public final |java.util.Collection| getWaitingThreads(java.util.concurrent.locks.AbstractQueuedSynchronizer.ConditionObject condition)

Returns a collection containing those threads that may be waiting on the given 
condition associated with this synchronizer. 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. 

    condition - the condition 

    Returns: the collection of threads 
*java.util.concurrent.locks.AbstractQueuedSynchronizer.getWaitQueueLength(AbstractQueuedSynchronizer.ConditionObject)*

public final int getWaitQueueLength(java.util.concurrent.locks.AbstractQueuedSynchronizer.ConditionObject condition)

Returns an estimate of the number of threads waiting on the given condition 
associated with this synchronizer. 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. 

    condition - the condition 

    Returns: the estimated number of waiting threads. 
*java.util.concurrent.locks.AbstractQueuedSynchronizer.hasContended()*

public final boolean hasContended()

Queries whether any threads have ever contended to acquire this synchronizer; 
that is if an acquire method has ever blocked. 

In this implementation, this operation returns in constant time. 


    Returns: true if there has ever been contention 
*java.util.concurrent.locks.AbstractQueuedSynchronizer.hasQueuedThreads()*

public final boolean hasQueuedThreads()

Queries whether any threads are waiting to acquire. Note that because 
cancellations due to interrupts and timeouts may occur at any time, a true 
return does not guarantee that any other thread will ever acquire. 

In this implementation, this operation returns in constant time. 


    Returns: true if there may be other threads waiting to acquire the lock. 
*java.util.concurrent.locks.AbstractQueuedSynchronizer.hasWaiters(AbstractQueuedSynchronizer.ConditionObject)*

public final boolean hasWaiters(java.util.concurrent.locks.AbstractQueuedSynchronizer.ConditionObject condition)

Queries whether any threads are waiting on the given condition associated with 
this synchronizer. 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. 

    condition - the condition 

    Returns: true if there are any waiting threads. 
*java.util.concurrent.locks.AbstractQueuedSynchronizer.isHeldExclusively()*

protected boolean isHeldExclusively()

Returns true if synchronization is held exclusively with respect to the current 
(calling) thread. This method is invoked upon each call to a non-waiting 
(|java.util.concurrent.locks.AbstractQueuedSynchronizer.ConditionObject|) 
method. (Waiting methods instead invoke 
(|java.util.concurrent.locks.AbstractQueuedSynchronizer|) .) The default 
implementation throws (|java.lang.UnsupportedOperationException|) . This method 
is invoked internally only within 
(|java.util.concurrent.locks.AbstractQueuedSynchronizer.ConditionObject|) 
methods, so need not be defined if conditions are not used. 


    Returns: true if synchronization is held exclusively; else false 
*java.util.concurrent.locks.AbstractQueuedSynchronizer.isQueued(Thread)*

public final boolean isQueued(java.lang.Thread thread)

Returns true if the given thread is currently queued. 

This implementation traverses the queue to determine presence of the given 
thread. 

    thread - the thread 

    Returns: true if the given thread in on the queue 
*java.util.concurrent.locks.AbstractQueuedSynchronizer.owns(AbstractQueuedSynchronizer.ConditionObject)*

public final boolean owns(java.util.concurrent.locks.AbstractQueuedSynchronizer.ConditionObject condition)

Queries whether the given ConditionObject uses this synchronizer as its lock. 

    condition - the condition 

    Returns: true if owned 
*java.util.concurrent.locks.AbstractQueuedSynchronizer.release(int)*

public final boolean release(int arg)

Releases in exclusive mode. Implemented by unblocking one or more threads if 
(|java.util.concurrent.locks.AbstractQueuedSynchronizer|) returns true. This 
method can be used to implement method (|java.util.concurrent.locks.Lock|) 

    arg - the release argument. This value is conveyed to {@link #tryRelease} but is 
       otherwise uninterpreted and can represent anything you like. 

    Returns: the value returned from {@link #tryRelease} 
*java.util.concurrent.locks.AbstractQueuedSynchronizer.releaseShared(int)*

public final boolean releaseShared(int arg)

Releases in shared mode. Implemented by unblocking one or more threads if 
(|java.util.concurrent.locks.AbstractQueuedSynchronizer|) returns true. 

    arg - the release argument. This value is conveyed to {@link #tryReleaseShared} but 
       is otherwise uninterpreted and can represent anything you like. 

    Returns: the value returned from {@link #tryReleaseShared} 
*java.util.concurrent.locks.AbstractQueuedSynchronizer.setState(int)*

protected final void setState(int newState)

Sets the value of synchronization state. This operation has memory semantics of 
a volatile write. 

    newState - the new state value 

*java.util.concurrent.locks.AbstractQueuedSynchronizer.toString()*

public |java.lang.String| toString()

Returns a string identifying this synchronizer, as well as its state. The 
state, in brackets, includes the String State = followed by the current value 
of (|java.util.concurrent.locks.AbstractQueuedSynchronizer|) , and either 
nonempty or empty depending on whether the queue is empty. 


    Returns: a string identifying this synchronizer, as well as its state. 
*java.util.concurrent.locks.AbstractQueuedSynchronizer.tryAcquire(int)*

protected boolean tryAcquire(int arg)

Attempts to acquire in exclusive mode. This method should query if the state of 
the object permits it to be acquired in the exclusive mode, and if so to 
acquire it. 

This method is always invoked by the thread performing acquire. If this method 
reports failure, the acquire method may queue the thread, if it is not already 
queued, until it is signalled by a release from some other thread. This can be 
used to implement method (|java.util.concurrent.locks.Lock|) . 

The default implementation throws (|java.lang.UnsupportedOperationException|) 

    arg - the acquire argument. This value is always the one passed to an acquire method, 
       or is the value saved on entry to a condition wait. The value is 
       otherwise uninterpreted and can represent anything you like. 

    Returns: true if successful. Upon success, this object has been acquired. 
*java.util.concurrent.locks.AbstractQueuedSynchronizer.tryAcquireNanos(int,long)*

public final boolean tryAcquireNanos(
  int arg,
  long nanosTimeout)
  throws |java.lang.InterruptedException|
         
Attempts to acquire in exclusive mode, aborting if interrupted, and failing if 
the given timeout elapses. Implemented by first checking interrupt status, then 
invoking at least once 
(|java.util.concurrent.locks.AbstractQueuedSynchronizer|) , returning on 
success. Otherwise, the thread is queued, possibly repeatedly blocking and 
unblocking, invoking (|java.util.concurrent.locks.AbstractQueuedSynchronizer|) 
until success or the thread is interrupted or the timeout elapses. This method 
can be used to implement method (|java.util.concurrent.locks.Lock|) . 

    arg - the acquire argument. This value is conveyed to {@link #tryAcquire} but is 
       otherwise uninterpreted and can represent anything you like. 
    nanosTimeout - the maximum number of nanoseconds to wait 

    Returns: true if acquired; false if timed out 
*java.util.concurrent.locks.AbstractQueuedSynchronizer.tryAcquireShared(int)*

protected int tryAcquireShared(int arg)

Attempts to acquire in shared mode. This method should query if the state of 
the object permits it to be acquired in the shared mode, and if so to acquire 
it. 

This method is always invoked by the thread performing acquire. If this method 
reports failure, the acquire method may queue the thread, if it is not already 
queued, until it is signalled by a release from some other thread. 

The default implementation throws (|java.lang.UnsupportedOperationException|) 

    arg - the acquire argument. This value is always the one passed to an acquire method, 
       or is the value saved on entry to a condition wait. The value is 
       otherwise uninterpreted and can represent anything you like. 

    Returns: a negative value on failure, zero on exclusive success, and a positive value if 
             non-exclusively successful, in which case a subsequent waiting 
             thread must check availability. (Support for three different 
             return values enables this method to be used in contexts where 
             acquires only sometimes act exclusively.) Upon success, this 
             object has been acquired. 
*java.util.concurrent.locks.AbstractQueuedSynchronizer.tryAcquireSharedNanos(int,long)*

public final boolean tryAcquireSharedNanos(
  int arg,
  long nanosTimeout)
  throws |java.lang.InterruptedException|
         
Attempts to acquire in shared mode, aborting if interrupted, and failing if the 
given timeout elapses. Implemented by first checking interrupt status, then 
invoking at least once 
(|java.util.concurrent.locks.AbstractQueuedSynchronizer|) , returning on 
success. Otherwise, the thread is queued, possibly repeatedly blocking and 
unblocking, invoking (|java.util.concurrent.locks.AbstractQueuedSynchronizer|) 
until success or the thread is interrupted or the timeout elapses. 

    arg - the acquire argument. This value is conveyed to {@link #tryAcquireShared} but 
       is otherwise uninterpreted and can represent anything you like. 
    nanosTimeout - the maximum number of nanoseconds to wait 

    Returns: true if acquired; false if timed out 
*java.util.concurrent.locks.AbstractQueuedSynchronizer.tryRelease(int)*

protected boolean tryRelease(int arg)

Attempts to set the state to reflect a release in exclusive mode. This method 
is always invoked by the thread performing release. 

The default implementation throws (|java.lang.UnsupportedOperationException|) 

    arg - the release argument. This value is always the one passed to a release method, 
       or the current state value upon entry to a condition wait. The value is 
       otherwise uninterpreted and can represent anything you like. 

    Returns: true if this object is now in a fully released state, so that any waiting 
             threads may attempt to acquire; and false otherwise. 
*java.util.concurrent.locks.AbstractQueuedSynchronizer.tryReleaseShared(int)*

protected boolean tryReleaseShared(int arg)

Attempts to set the state to reflect a release in shared mode. This method is 
always invoked by the thread performing release. The default implementation 
throws (|java.lang.UnsupportedOperationException|) 

    arg - the release argument. This value is always the one passed to a release method, 
       or the current state value upon entry to a condition wait. The value is 
       otherwise uninterpreted and can represent anything you like. 

    Returns: true if this object is now in a fully released state, so that any waiting 
             threads may attempt to acquire; and false otherwise.