public class ListenableFutureTask<V> extends FutureTask<V> implements ListenableFuture<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)
.
Modifier and Type | Method and Description |
---|---|
void |
addListener(Runnable listener,
Executor exec)
Registers a listener to be run on
the given executor.
|
static <V> ListenableFutureTask<V> |
create(Callable<V> callable)
Creates a
ListenableFutureTask that will upon running, execute the
given Callable . |
static <V> ListenableFutureTask<V> |
create(Runnable runnable,
V result)
Creates a
ListenableFutureTask that will upon running, execute the
given Runnable , and arrange that get will return the
given result on successful completion. |
protected void |
done()
Internal implementation detail used to invoke the listeners.
|
cancel, get, get, isCancelled, isDone, run, runAndReset, set, setException
public static <V> ListenableFutureTask<V> create(Callable<V> callable)
ListenableFutureTask
that will upon running, execute the
given Callable
.callable
- the callable taskpublic static <V> ListenableFutureTask<V> create(Runnable runnable, @Nullable V result)
ListenableFutureTask
that will upon running, execute the
given Runnable
, and arrange that get
will return the
given result on successful completion.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)
public void addListener(Runnable listener, Executor exec)
ListenableFuture
Future
'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., a RejectedExecutionException
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. Heavyweight directExecutor
listeners can cause problems, and
these problems can be difficult to reproduce because they depend on timing.
For example:
addListener
. That
caller may be a UI thread or other latency-sensitive thread. This can harm
UI responsiveness.
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.
directExecutor
listeners.
This is the most general listener interface. For common operations
performed using listeners, see Futures
. For a simplified but
general listener interface, see addCallback()
.
Memory consistency effects: Actions in a thread prior to adding a listener happen-before its execution begins, perhaps in another thread.
addListener
in interface ListenableFuture<V>
listener
- the listener to run when the computation is completeexec
- the executor to run the listener inprotected void done()
done
in class FutureTask<V>
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