| ReentrantLock | java.util.concurrent.locks |
This class implements the
Lock interface and adds instrumentation methods to
determine what thread currently holds the lock, to return the number
of threads waiting to acquire the lock or waiting on an associated
Condition, and to test whether a specified thread
is waiting to acquire the lock.The name of this class includes the term
"reentrant" because the thread that
holds the lock can call any of the locking methods again, and they
return immediately without blocking. isHeldByCurrentThread(
) tests whether the current thread already holds the lock.
getHoldCount( ) returns the number of times that
the current thread has acquired this lock. unlock(
) must be called this number of times before the lock is
actually relinquished.A "fair" lock may be created by
passing true to the ReentrantLock(
) constructor. If you do this, the lock will always be
granted to the thread that has been waiting for it the longest.
Figure 16-105. java.util.concurrent.locks.ReentrantLock
 public class ReentrantLock implements Lock, Serializable {
// Public Constructors
public ReentrantLock ( );
public ReentrantLock (boolean fair );
// Public Instance Methods
public int getHoldCount ( ); default:0
public final int getQueueLength ( ); default:0
public int getWaitQueueLength (Condition condition );
public final boolean hasQueuedThread (Thread thread );
public final boolean hasQueuedThreads ( );
public boolean hasWaiters (Condition condition );
public final boolean isFair ( ); default:false
public boolean isHeldByCurrentThread ( ); default:false
public boolean isLocked ( ); default:false
// Methods Implementing Lock
public void lock ( );
public void lockInterruptibly ( ) throws InterruptedException;
public Condition newCondition ( );
public boolean tryLock ( );
public boolean tryLock (long timeout , java.util.concurrent.TimeUnit unit )
throws InterruptedException;
public void unlock ( );
// Public Methods Overriding Object
public String toString ( );
// Protected Instance Methods
protected Thread getOwner ( );
protected java.util.Collection<Thread> getQueuedThreads ( );
protected java.util.Collection<Thread> getWaitingThreads (Condition condition );
}
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