EDU.oswego.cs.dl.util.concurrent
Class ReentrantLock

java.lang.Object
  EDU.oswego.cs.dl.util.concurrent.ReentrantLock

All Implemented Interfaces:

Sync

public class ReentrantLock
extends java.lang.Object
implements Sync

A lock with the same semantics as builtin Java synchronized locks: Once a thread has a lock, it can re-obtain it any number of times without blocking. The lock is made available to other threads when as many releases as acquires have occurred.

[ Introduction to this package. ]

Field Summary

protected long	holds_
protected java.lang.Thread	owner_

Fields inherited from interface EDU.oswego.cs.dl.util.concurrent.Sync

ONE_CENTURY, ONE_DAY, ONE_HOUR, ONE_MINUTE, ONE_SECOND, ONE_WEEK, ONE_YEAR

Constructor Summary

ReentrantLock()

Method Summary

void	acquire() Wait (possibly forever) until successful passage.
boolean	attempt(long msecs) Wait at most msecs to pass; report whether passed.
long	holds() Return the number of unreleased acquires performed by the current thread.
void	release() Release the lock.
void	release(long n) Release the lock N times.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Field Detail

owner_

protected java.lang.Thread owner_

holds_

protected long holds_

Constructor Detail

ReentrantLock

public ReentrantLock()

Method Detail

acquire

public void acquire()
             throws java.lang.InterruptedException

Description copied from interface: Sync

Wait (possibly forever) until successful passage. Fail only upon interuption. Interruptions always result in `clean' failures. On failure, you can be sure that it has not been acquired, and that no corresponding release should be performed. Conversely, a normal return guarantees that the acquire was successful.

Specified by:

acquire in interface Sync

Throws:

java.lang.InterruptedException

attempt

public boolean attempt(long msecs)
                throws java.lang.InterruptedException

Description copied from interface: Sync

Wait at most msecs to pass; report whether passed.

The method has best-effort semantics: The msecs bound cannot be guaranteed to be a precise upper bound on wait time in Java. Implementations generally can only attempt to return as soon as possible after the specified bound. Also, timers in Java do not stop during garbage collection, so timeouts can occur just because a GC intervened. So, msecs arguments should be used in a coarse-grained manner. Further, implementations cannot always guarantee that this method will return at all without blocking indefinitely when used in unintended ways. For example, deadlocks may be encountered when called in an unintended context.

Specified by:

attempt in interface Sync

Parameters:

msecs - the number of milleseconds to wait. An argument less than or equal to zero means not to wait at all. However, this may still require access to a synchronization lock, which can impose unbounded delay if there is a lot of contention among threads.

Returns:

true if acquired

Throws:

java.lang.InterruptedException

release

public void release()

Release the lock.

Specified by:

release in interface Sync

Throws:

java.lang.Error - thrown if not current owner of lock

release

public void release(long n)

Release the lock N times. release(n) is equivalent in effect to:

   for (int i = 0; i < n; ++i) release();
 

Throws:

java.lang.Error - thrown if not current owner of lock or has fewer than N holds on the lock

holds

public long holds()

Return the number of unreleased acquires performed by the current thread. Returns zero if current thread does not hold lock.