- java.lang.Object
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- com.google.common.util.concurrent.internal.InternalFutureFailureAccess
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- com.google.common.util.concurrent.AbstractFuture<V>
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- com.google.common.util.concurrent.SettableFuture<V>
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- All Implemented Interfaces:
ListenableFuture<V>
,Future<V>
@GwtCompatible public final class SettableFuture<V extends @Nullable Object> extends AbstractFuture<V>
AListenableFuture
whose result can be set by aset(Object)
,setException(Throwable)
orsetFuture(ListenableFuture)
call. It can also, like any otherFuture
, be cancelled.SettableFuture
is the recommendedListenableFuture
implementation when your task cannot be implemented withListeningExecutorService
, the variousFutures
utility methods, orListenableFutureTask
. Those APIs have less opportunity for developer error. If your needs are more complex thanSettableFuture
supports, useAbstractFuture
, which offers an extensible version of the API.- Since:
- 9.0 (in 1.0 as
ValueFuture
) - Author:
- Sven Mawson
-
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Method Summary
All Methods Static Methods Instance Methods Concrete Methods Modifier and Type Method 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 extends @Nullable Object>
SettableFuture<V>create()
Creates a newSettableFuture
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()
Returnstrue
if this task was cancelled before it completed normally.boolean
isDone()
Returnstrue
if this task completed.boolean
set(V value)
Sets the result of thisFuture
unless thisFuture
has already been cancelled or set (including set asynchronously).boolean
setException(Throwable throwable)
Sets the failed result of thisFuture
unless thisFuture
has already been cancelled or set (including set asynchronously).boolean
setFuture(ListenableFuture<? extends V> future)
Sets the result of thisFuture
to match the supplied inputFuture
once the suppliedFuture
is done, unless thisFuture
has already been cancelled or set (including "set asynchronously," defined below).-
Methods inherited from class com.google.common.util.concurrent.AbstractFuture
afterDone, interruptTask, pendingToString, toString, tryInternalFastPathGetFailure, wasInterrupted
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Method Detail
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create
public static <V extends @Nullable Object> SettableFuture<V> create()
Creates a newSettableFuture
that can be completed or cancelled by a later method call.
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set
@CanIgnoreReturnValue public boolean set(V value)
Description copied from class:AbstractFuture
Sets the result of thisFuture
unless thisFuture
has already been cancelled or set (including set asynchronously). When a call to this method returns, theFuture
is guaranteed to be done only if the call was accepted (in which case it returnstrue
). If it returnsfalse
, theFuture
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 aset*
method, only by a call toAbstractFuture.cancel(boolean)
.Beware of completing a future while holding a lock. Its listeners may do slow work or acquire other locks, risking deadlocks.
- Overrides:
set
in classAbstractFuture<V extends @Nullable Object>
- Parameters:
value
- the value to be used as the result- Returns:
- true if the attempt was accepted, completing the
Future
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setException
@CanIgnoreReturnValue public boolean setException(Throwable throwable)
Description copied from class:AbstractFuture
Sets the failed result of thisFuture
unless thisFuture
has already been cancelled or set (including set asynchronously). When a call to this method returns, theFuture
is guaranteed to be done only if the call was accepted (in which case it returnstrue
). If it returnsfalse
, theFuture
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 aset*
method, only by a call toAbstractFuture.cancel(boolean)
.Beware of completing a future while holding a lock. Its listeners may do slow work or acquire other locks, risking deadlocks.
- Overrides:
setException
in classAbstractFuture<V extends @Nullable Object>
- Parameters:
throwable
- the exception to be used as the failed result- Returns:
- true if the attempt was accepted, completing the
Future
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setFuture
@CanIgnoreReturnValue public boolean setFuture(ListenableFuture<? extends V> future)
Description copied from class:AbstractFuture
Sets the result of thisFuture
to match the supplied inputFuture
once the suppliedFuture
is done, unless thisFuture
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 toAbstractFuture.cancel(boolean)
.If the call
setFuture(delegate)
is accepted and thisFuture
is later cancelled, cancellation will be propagated todelegate
. Additionally, any call tosetFuture
after any cancellation will propagate cancellation to the suppliedFuture
.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 theAbstractFuture.wasInterrupted()
method will not returntrue
.Beware of completing a future while holding a lock. Its listeners may do slow work or acquire other locks, risking deadlocks.
- Overrides:
setFuture
in classAbstractFuture<V extends @Nullable Object>
- Parameters:
future
- the future to delegate to- Returns:
- true if the attempt was accepted, indicating that the
Future
was not previously cancelled or set.
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get
@CanIgnoreReturnValue public final V get() throws InterruptedException, ExecutionException
Description copied from class:AbstractFuture
Waits if necessary for the computation to complete, and then retrieves its result.The default
AbstractFuture
implementation throwsInterruptedException
if the current thread is interrupted during the call, even if the value is already available.- Specified by:
get
in interfaceFuture<V extends @Nullable Object>
- Overrides:
get
in classAbstractFuture<V extends @Nullable Object>
- Returns:
- the computed result
- Throws:
InterruptedException
- if the current thread was interrupted while waitingExecutionException
- if the computation threw an exception
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get
@CanIgnoreReturnValue public final V get(long timeout, TimeUnit unit) throws InterruptedException, ExecutionException, TimeoutException
Description copied from class:AbstractFuture
Waits if necessary for at most the given time for the computation to complete, and then retrieves its result, if available.The default
AbstractFuture
implementation throwsInterruptedException
if the current thread is interrupted during the call, even if the value is already available.- Specified by:
get
in interfaceFuture<V extends @Nullable Object>
- Overrides:
get
in classAbstractFuture<V extends @Nullable Object>
- Parameters:
timeout
- the maximum time to waitunit
- the time unit of the timeout argument- Returns:
- the computed result
- Throws:
InterruptedException
- if the current thread was interrupted while waitingExecutionException
- if the computation threw an exceptionTimeoutException
- if the wait timed out
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isDone
public final boolean isDone()
Description copied from interface:java.util.concurrent.Future
Returnstrue
if this task completed. Completion may be due to normal termination, an exception, or cancellation -- in all of these cases, this method will returntrue
.
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isCancelled
public final boolean isCancelled()
Description copied from interface:java.util.concurrent.Future
Returnstrue
if this task was cancelled before it completed normally.- Specified by:
isCancelled
in interfaceFuture<V extends @Nullable Object>
- Overrides:
isCancelled
in classAbstractFuture<V extends @Nullable Object>
- Returns:
true
if this task was cancelled before it completed
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addListener
public final void addListener(Runnable listener, Executor executor)
Description copied from class:AbstractFuture
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: If your listener is lightweight -- and will not cause stack overflow by completing more futures or adding more
directExecutor()
listeners inline -- considerMoreExecutors.directExecutor()
. Otherwise, avoid it: See the warnings on the docs fordirectExecutor
.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.
Guava implementations of
ListenableFuture
promptly release references to listeners after executing them.- Specified by:
addListener
in interfaceListenableFuture<V extends @Nullable Object>
- Overrides:
addListener
in classAbstractFuture<V extends @Nullable Object>
- Parameters:
listener
- the listener to run when the computation is completeexecutor
- the executor to run the listener in
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cancel
@CanIgnoreReturnValue public final boolean cancel(boolean mayInterruptIfRunning)
Description copied from class:AbstractFuture
Attempts to cancel execution of this task. This attempt will fail if the task has already completed, has already been cancelled, or could not be cancelled for some other reason. If successful, and this task has not started whencancel
is called, this task should never run. If the task has already started, then themayInterruptIfRunning
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 returntrue
. Subsequent calls toFuture.isCancelled()
will always returntrue
if this method returnedtrue
.If a cancellation attempt succeeds on a
Future
that had previously been set asynchronously, then the cancellation will also be propagated to the delegateFuture
that was supplied in thesetFuture
call.Rather than override this method to perform additional cancellation work or cleanup, subclasses should override
AbstractFuture.afterDone()
, consultingAbstractFuture.isCancelled()
andAbstractFuture.wasInterrupted()
as necessary. This ensures that the work is done even if the future is cancelled without a call tocancel
, such as by callingsetFuture(cancelledFuture)
.Beware of completing a future while holding a lock. Its listeners may do slow work or acquire other locks, risking deadlocks.
- Specified by:
cancel
in interfaceFuture<V extends @Nullable Object>
- Overrides:
cancel
in classAbstractFuture<V extends @Nullable Object>
- Parameters:
mayInterruptIfRunning
-true
if the thread executing this task should be interrupted; otherwise, in-progress tasks are allowed to complete- Returns:
false
if the task could not be cancelled, typically because it has already completed normally;true
otherwise
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