groovyx.gpars.dataflow.impl
Class ResizeableCountDownLatch

java.lang.Object
  groovyx.gpars.dataflow.impl.ResizeableCountDownLatch

public final class ResizeableCountDownLatch
extends java.lang.Object

CountDownLatch with the ability to change the number of waiting parties

Author:

Vaclav Pech, Doug Lea

Nested Class Summary

private static class

ResizeableCountDownLatch.Sync Synchronization control For CountDownLatch.

Field Summary

private ResizeableCountDownLatch.Sync

sync

Constructor Summary

ResizeableCountDownLatch(int count)
Constructs a CountDownLatch initialized with the given count.

Method Summary

boolean	attemptToCountDownAndAwait(long timeout) Attempts to atomically count down the latch and await release with a timeout.
void	await() Causes the current thread to wait until the latch has counted down to zero, unless the thread is interrupted.
boolean	await(long timeout, java.util.concurrent.TimeUnit unit) Causes the current thread to wait until the latch has counted down to zero, unless the thread is interrupted, or the specified waiting time elapses.
void	countDown() Decrements the count of the latch, releasing all waiting threads if the count reaches zero.
void	decreaseCount()
long	getCount() Returns the current count.
void	increaseCount()
boolean	isReleasedFlag()
java.lang.String	toString() Returns a string identifying this latch, as well as its state.

Methods inherited from class java.lang.Object

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

Field Detail

sync

private final ResizeableCountDownLatch.Sync sync

Constructor Detail

ResizeableCountDownLatch

public ResizeableCountDownLatch(int count)

Constructs a CountDownLatch initialized with the given count.

Parameters:

count - the number of times countDown() must be invoked before threads can pass through await()

Throws:

java.lang.IllegalArgumentException - if count is negative

Method Detail

await

public void await()
           throws java.lang.InterruptedException

Causes the current thread to wait until the latch has counted down to zero, unless the thread is interrupted.

If the current count is zero then this method returns immediately.

If the current count is greater than zero then the current thread becomes disabled for thread scheduling purposes and lies dormant until one of two things happen:

• The count reaches zero due to invocations of the countDown() method; or
• Some other thread interrupts the current thread.

If the current thread:

• has its interrupted status set on entry to this method; or
• is interrupted while waiting,

then InterruptedException is thrown and the current thread's interrupted status is cleared.

Throws:

java.lang.InterruptedException - if the current thread is interrupted while waiting

await

public boolean await(long timeout,
                     java.util.concurrent.TimeUnit unit)
              throws java.lang.InterruptedException

Causes the current thread to wait until the latch has counted down to zero, unless the thread is interrupted, or the specified waiting time elapses.

If the current count is zero then this method returns immediately with the value true.

If the current count is greater than zero then the current thread becomes disabled for thread scheduling purposes and lies dormant until one of three things happen:

• The count reaches zero due to invocations of the countDown() method; or
• Some other thread interrupts the current thread; or
• The specified waiting time elapses.

If the count reaches zero then the method returns with the value true.

If the current thread:

• has its interrupted status set on entry to this method; or
• is interrupted while waiting,

then 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.

Parameters:

timeout - the maximum time to wait

unit - the time unit of the timeout argument

Returns:

true if the count reached zero and false if the waiting time elapsed before the count reached zero

Throws:

java.lang.InterruptedException - if the current thread is interrupted while waiting

attemptToCountDownAndAwait

public boolean attemptToCountDownAndAwait(long timeout)
                                   throws java.lang.InterruptedException

Attempts to atomically count down the latch and await release with a timeout. If the timeout expires, the count is increased and the latch is re-tested before reporting failed timeout.

Parameters:

timeout - The time in nanoseconds to await

Returns:

True, if successful, false, is the timeout elapses without the latch being released

Throws:

java.lang.InterruptedException - If the thread gets interrupted while waiting for the release

isReleasedFlag

public boolean isReleasedFlag()

countDown

public void countDown()

Decrements the count of the latch, releasing all waiting threads if the count reaches zero.

If the current count is greater than zero then it is decremented. If the new count is zero then all waiting threads are re-enabled for thread scheduling purposes.

If the current count equals zero then nothing happens.

increaseCount

public void increaseCount()

decreaseCount

public void decreaseCount()

getCount

public long getCount()

Returns the current count.

This method is typically used for debugging and testing purposes.

Returns:

the current count

toString

public java.lang.String toString()

Returns a string identifying this latch, as well as its state. The state, in brackets, includes the String "Count =" followed by the current count.

Overrides:

toString in class java.lang.Object

Returns:

a string identifying this latch, as well as its state