@GwtCompatible public final class SettableFuture<V> extends AbstractFuture<V>
ListenableFuture whose result can be set by a set(Object), setException(Throwable) or setFuture(ListenableFuture) call. It can also, like any
other Future, be cancelled.
SettableFuture is the recommended ListenableFuture implementation when your
task cannot be implemented with ListeningExecutorService, the various Futures
utility methods, or ListenableFutureTask. Those APIs have less opportunity for developer
error. If your needs are more complex than SettableFuture supports, use
AbstractFuture, which offers an extensible version of the API.
ValueFuture)| Modifier and Type | Method and Description |
|---|---|
void |
addListener(Runnable listener,
Executor executor)
Registers a listener to be run on the given executor.
|
boolean |
cancel(boolean mayInterruptIfRunning)
Attempts to cancel execution of this task.
|
static <V> SettableFuture<V> |
create()
Creates a new
SettableFuture that can be completed or cancelled by a later method call. |
V |
get()
Waits if necessary for the computation to complete, and then
retrieves its result.
|
V |
get(long timeout,
TimeUnit unit)
Waits if necessary for at most the given time for the computation
to complete, and then retrieves its result, if available.
|
boolean |
isCancelled()
Returns
true if this task was cancelled before it completed
normally. |
boolean |
isDone()
Returns
true if this task completed. |
boolean |
set(V value)
Sets the result of this
Future unless this Future has already been cancelled or
set (including set asynchronously). |
boolean |
setException(Throwable throwable)
Sets the failed result of this
Future unless this Future has already been
cancelled or set (including set asynchronously). |
boolean |
setFuture(ListenableFuture<? extends V> future)
Sets the result of this
Future to match the supplied input Future once the
supplied Future is done, unless this Future has already been cancelled or set
(including "set asynchronously," defined below). |
afterDone, interruptTask, pendingToString, toString, wasInterruptedaddCallback, catching, catchingAsync, from, transform, transformAsync, withTimeoutpublic static <V> SettableFuture<V> create()
SettableFuture that can be completed or cancelled by a later method call.public boolean set(@Nullable V value)
AbstractFutureFuture unless this Future has already been cancelled or
set (including set asynchronously). When a call to this method returns,
the Future is guaranteed to be done only if the call was
accepted (in which case it returns true). If it returns false, the Future may have previously been set asynchronously, in which case its result may not be known
yet. That result, though not yet known, cannot be overridden by a call to a set*
method, only by a call to AbstractFuture.cancel(boolean).set in class AbstractFuture<V>value - the value to be used as the resultFuturepublic boolean setException(Throwable throwable)
AbstractFutureFuture unless this Future has already been
cancelled or set (including set asynchronously). When a call to this
method returns, the Future is guaranteed to be done only if
the call was accepted (in which case it returns true). If it returns false, the
Future may have previously been set asynchronously, in which case its result may not be
known yet. That result, though not yet known, cannot be overridden by a call to a set*
method, only by a call to AbstractFuture.cancel(boolean).setException in class AbstractFuture<V>throwable - the exception to be used as the failed resultFuture@Beta public boolean setFuture(ListenableFuture<? extends V> future)
AbstractFutureFuture to match the supplied input Future once the
supplied Future is done, unless this Future has already been cancelled or set
(including "set asynchronously," defined below).
If the supplied future is done when this method is called and the call
is accepted, then this future is guaranteed to have been completed with the supplied future by
the time this method returns. If the supplied future is not done and the call is accepted, then
the future will be set asynchronously. Note that such a result, though not yet known,
cannot be overridden by a call to a set* method, only by a call to AbstractFuture.cancel(boolean).
If the call setFuture(delegate) is accepted and this Future is later
cancelled, cancellation will be propagated to delegate. Additionally, any call to
setFuture after any cancellation will propagate cancellation to the supplied Future.
Note that, even if the supplied future is cancelled and it causes this future to complete,
it will never trigger interruption behavior. In particular, it will not cause this future to
invoke the AbstractFuture.interruptTask() method, and the AbstractFuture.wasInterrupted() method will not
return true.
setFuture in class AbstractFuture<V>future - the future to delegate toFuture was not previously
cancelled or set.public final V get() throws InterruptedException, ExecutionException
AbstractFutureThe default AbstractFuture implementation throws InterruptedException if the
current thread is interrupted during the call, even if the value is already available.
get in interface Future<V>get in class AbstractFuture<V>InterruptedException - if the current thread was interrupted
while waitingExecutionException - if the computation threw an
exceptionpublic final V get(long timeout, TimeUnit unit) throws InterruptedException, ExecutionException, TimeoutException
AbstractFutureThe default AbstractFuture implementation throws InterruptedException if the
current thread is interrupted during the call, even if the value is already available.
get in interface Future<V>get in class AbstractFuture<V>timeout - the maximum time to waitunit - the time unit of the timeout argumentInterruptedException - if the current thread was interrupted
while waitingExecutionException - if the computation threw an
exceptionTimeoutException - if the wait timed outpublic final boolean isDone()
java.util.concurrent.Futuretrue if this task completed.
Completion may be due to normal termination, an exception, or
cancellation -- in all of these cases, this method will return
true.isDone in interface Future<V>isDone in class AbstractFuture<V>true if this task completedpublic final boolean isCancelled()
java.util.concurrent.Futuretrue if this task was cancelled before it completed
normally.isCancelled in interface Future<V>isCancelled in class AbstractFuture<V>true if this task was cancelled before it completedpublic final void addListener(Runnable listener, Executor executor)
AbstractFutureFuture'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>addListener in class AbstractFuture<V>listener - the listener to run when the computation is completeexecutor - the executor to run the listener inpublic final boolean cancel(boolean mayInterruptIfRunning)
AbstractFuturecancel is called,
this task should never run. If the task has already started,
then the mayInterruptIfRunning parameter determines
whether the thread executing this task should be interrupted in
an attempt to stop the task.
After this method returns, subsequent calls to Future.isDone() will
always return true. Subsequent calls to Future.isCancelled()
will always return true if this method returned true.
If a cancellation attempt succeeds on a Future that had previously been set asynchronously, then the cancellation will also be propagated to the delegate
Future that was supplied in the setFuture call.
Rather than override this method to perform additional cancellation work or cleanup,
subclasses should override AbstractFuture.afterDone(), consulting AbstractFuture.isCancelled() and AbstractFuture.wasInterrupted() as necessary. This ensures that the work is done even if the future is
cancelled without a call to cancel, such as by calling setFuture(cancelledFuture).
cancel in interface Future<V>cancel in class AbstractFuture<V>mayInterruptIfRunning - true if the thread executing this
task should be interrupted; otherwise, in-progress tasks are allowed
to completefalse if the task could not be cancelled,
typically because it has already completed normally;
true otherwiseCopyright © 2010–2017. All rights reserved.