GoogleCodeExporter
commented
9 years ago Here is a sample implementation using joda-time (easily replaced):
/**
* A future with a predetermined execution path.
*
* @param <V> the return type of the Future
*/
public class PredeterminedFuture<V> implements Future<V>
{
private boolean cancelled;
private boolean done;
private final V value;
private final Throwable throwable;
private final DateTime publishTime;
/**
* Creates a new PredeterminedFuture.
*
* If <code>throwable</code> is non-null, the Future will throw the exception; otherwise,
* it return the value.
*
* @param value the value to return
* @param throwable the Throwable to throw
* @param timeout the amount of time to wait before publishing the result
* @param unit the unit of timeout
*/
public PredeterminedFuture(V value, Throwable throwable, long timeout, TimeUnit unit)
{
this.value = value;
this.throwable = throwable;
if (timeout == Long.MAX_VALUE)
{
// never publish the result
this.publishTime = null;
}
else
this.publishTime = new DateTime(unit.toMillis(timeout));
}
@Override
public synchronized boolean cancel(boolean mayInterruptIfRunning)
{
if (publishTime == null || publishTime.isAfterNow())
{
cancelled = true;
done = true;
notifyAll();
}
return cancelled;
}
@Override
public synchronized boolean isCancelled()
{
return cancelled;
}
@Override
public synchronized boolean isDone()
{
return done;
}
/**
* Waits until the Future is done or times out.
*
* @param wakeupTime indicates when to return even if <code>done</code> is false, null of
* the method should wait for <code>done</code>
* @throws InterruptedException if the thread is interrupted
*/
private synchronized void waitUntil(DateTime wakeupTime) throws InterruptedException
{
while (!done)
{
long timeLeft;
if (wakeupTime == null)
timeLeft = Long.MAX_VALUE;
else
{
DateTime now = new DateTime();
timeLeft = new Duration(now, wakeupTime).getMillis();
}
if (timeLeft <= 0)
{
done = true;
break;
}
TimeUnit.MILLISECONDS.timedWait(this, timeLeft);
}
}
@Override
public synchronized V get() throws InterruptedException, ExecutionException
{
waitUntil(publishTime);
if (cancelled)
throw new CancellationException();
if (throwable != null)
throw new ExecutionException(throwable);
return value;
}
@Override
public synchronized V get(long timeout, TimeUnit unit) throws InterruptedException,
ExecutionException, TimeoutException
{
DateTime startTime = new DateTime();
DateTime earliestEvent = startTime.plus(unit.toMillis(timeout));
if (publishTime != null && publishTime.isBefore(earliestEvent))
earliestEvent = publishTime;
waitUntil(earliestEvent);
if (cancelled)
throw new CancellationException();
if (throwable != null)
throw new ExecutionException(throwable);
return value;
}
}
Original comment by cowwoc...@gmail.com on 23 Nov 2010 at 10:38
Original issue reported on code.google.com by
cowwoc...@gmail.comon 23 Nov 2010 at 9:32