Class ListenableFutureTask<V>
- All Implemented Interfaces:
ListenableFuture<V>
,Runnable
,Future<V>
,RunnableFuture<V>
FutureTask
that also implements the ListenableFuture
interface. Unlike
FutureTask
, ListenableFutureTask
does not provide an overrideable done()
method. For similar functionality, call addListener(java.lang.Runnable, java.util.concurrent.Executor)
.
Few users should use this class. It is intended primarily for those who are implementing an
ExecutorService
. Most users should call ListeningExecutorService.submit
on a service obtained from MoreExecutors.listeningDecorator(java.util.concurrent.ExecutorService)
.
- Since:
- 1.0
-
Nested Class Summary
Nested classes/interfaces inherited from interface java.util.concurrent.Future
Future.State
-
Method Summary
Modifier and TypeMethodDescriptionvoid
addListener
(Runnable listener, Executor exec) Registers a listener to be run on the given executor.static <V> ListenableFutureTask
<V> Creates aListenableFutureTask
that will upon running, execute the givenRunnable
, and arrange thatget
will return the given result on successful completion.static <V> ListenableFutureTask
<V> Creates aListenableFutureTask
that will upon running, execute the givenCallable
.protected void
done()
Internal implementation detail used to invoke the listeners.Methods inherited from class java.util.concurrent.FutureTask
cancel, exceptionNow, get, get, isCancelled, isDone, resultNow, run, runAndReset, set, setException, state, toString
Methods inherited from class java.lang.Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait
Methods inherited from interface java.util.concurrent.Future
cancel, exceptionNow, get, get, isCancelled, isDone, resultNow, state
-
Method Details
-
create
Creates aListenableFutureTask
that will upon running, execute the givenCallable
.- Parameters:
callable
- the callable task- Since:
- 10.0
-
create
Creates aListenableFutureTask
that will upon running, execute the givenRunnable
, and arrange thatget
will return the given result on successful completion.- Parameters:
runnable
- the runnable taskresult
- the result to return on successful completion. If you don't need a particular result, consider using constructions of the form:ListenableFuture<?> f = ListenableFutureTask.create(runnable, null)
- Since:
- 10.0
-
addListener
Description copied from interface:ListenableFuture
Registers a listener to be run on the given executor. The listener will run when theFuture
's computation is complete or, if the computation is already complete, immediately.There is no guaranteed ordering of execution of listeners, but any listener added through this method is guaranteed to be called once the computation is complete.
Exceptions thrown by a listener will be propagated up to the executor. Any exception thrown during
Executor.execute
(e.g., aRejectedExecutionException
or an exception thrown by direct execution) will be caught and logged.Note: For fast, lightweight listeners that would be safe to execute in any thread, consider
MoreExecutors.directExecutor()
. Otherwise, avoid it. HeavyweightdirectExecutor
listeners can cause problems, and these problems can be difficult to reproduce because they depend on timing. For example:- The listener may be executed by the caller of
addListener
. That caller may be a UI thread or other latency-sensitive thread. This can harm UI responsiveness. - The listener may be executed by the thread that completes this
Future
. That thread may be an internal system thread such as an RPC network thread. Blocking that thread may stall progress of the whole system. It may even cause a deadlock. - The listener may delay other listeners, even listeners that are not themselves
directExecutor
listeners.
This is the most general listener interface. For common operations performed using listeners, see
Futures
. For a simplified but general listener interface, seeaddCallback()
.Memory consistency effects: Actions in a thread prior to adding a listener happen-before its execution begins, perhaps in another thread.
- Specified by:
addListener
in interfaceListenableFuture<V>
- Parameters:
listener
- the listener to run when the computation is completeexec
- the executor to run the listener in
- The listener may be executed by the caller of
-
done
protected void done()Internal implementation detail used to invoke the listeners.- Overrides:
done
in classFutureTask<V>
-