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

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

All Implemented Interfaces:

Sync

public class TimeoutSync
extends java.lang.Object
implements Sync

A TimeoutSync is an adaptor class that transforms all calls to acquire to instead invoke attempt with a predetermined timeout value.

Sample Usage. A TimeoutSync can be used to obtain Timeouts for locks used in SyncCollections. For example:

 Mutex lock = new Mutex();
 TimeoutSync timedLock = new TimeoutSync(lock, 1000); // 1 sec timeouts
 Set set = new SyncSet(new HashSet(), timedlock);
 try {
   set. add("hi");
 }
 // SyncSets translate timeouts and other lock failures 
 //   to unsupported operation exceptions, 
 catch (UnsupportedOperationException ex) {
    System.out.println("Lock failure");
 }
 

[ Introduction to this package. ]

See Also:

Sync

Field Summary

protected Sync	sync_
protected long	timeout_

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

TimeoutSync(Sync sync, long timeout)
Create a TimeoutSync using the given Sync object, and using the given timeout value for all calls to acquire.

Method Summary

void	acquire() Wait (possibly forever) until successful passage.
boolean	attempt(long msecs) Wait at most msecs to pass; report whether passed.
void	release() Potentially enable others to pass.

Methods inherited from class java.lang.Object

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

Field Detail

sync_

protected final Sync sync_

timeout_

protected final long timeout_

Constructor Detail

TimeoutSync

public TimeoutSync(Sync sync,
                   long timeout)

Create a TimeoutSync using the given Sync object, and using the given timeout value for all calls to acquire.

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()

Description copied from interface: Sync

Potentially enable others to pass.

Because release does not raise exceptions, it can be used in `finally' clauses without requiring extra embedded try/catch blocks. But keep in mind that as with any java method, implementations may still throw unchecked exceptions such as Error or NullPointerException when faced with uncontinuable errors. However, these should normally only be caught by higher-level error handlers.

Specified by:

release in interface Sync