Class SettableFuture<V>
- java.lang.Object
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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>
,java.util.concurrent.Future<V>
@GwtCompatible public final class SettableFuture<V> 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 is not a good fit for aListeningExecutorService
task. 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
)
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Method Summary
All Methods Static Methods Instance Methods Concrete Methods Modifier and Type Method Description void
addListener(java.lang.Runnable listener, java.util.concurrent.Executor executor)
Registers a listener to be run on the given executor.boolean
cancel(boolean mayInterruptIfRunning)
static <V> SettableFuture<V>
create()
Creates a newSettableFuture
that can be completed or cancelled by a later method call.V
get()
V
get(long timeout, java.util.concurrent.TimeUnit unit)
boolean
isCancelled()
boolean
isDone()
boolean
set(V value)
Sets the result of thisFuture
unless thisFuture
has already been cancelled or set (including set asynchronously).boolean
setException(java.lang.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, wasInterrupted
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Method Detail
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create
public static <V> SettableFuture<V> create()
Creates a newSettableFuture
that can be completed or cancelled by a later method call.
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set
public boolean set(@Nullable 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 by overridden by a call to aset*
method, only by a call toAbstractFuture.cancel(boolean)
.- Overrides:
set
in classAbstractFuture<V>
- 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
public boolean setException(java.lang.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 by overridden by a call to aset*
method, only by a call toAbstractFuture.cancel(boolean)
.- Overrides:
setException
in classAbstractFuture<V>
- 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
@Beta 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 by 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
.- Overrides:
setFuture
in classAbstractFuture<V>
- 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
public final V get() throws java.lang.InterruptedException, java.util.concurrent.ExecutionException
Description copied from class:AbstractFuture
The default
AbstractFuture
implementation throwsInterruptedException
if the current thread is interrupted before or during the call, even if the value is already available.- Specified by:
get
in interfacejava.util.concurrent.Future<V>
- Overrides:
get
in classAbstractFuture<V>
- Throws:
java.lang.InterruptedException
- if the current thread was interrupted before or during the call (optional but recommended).java.util.concurrent.ExecutionException
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get
public final V get(long timeout, java.util.concurrent.TimeUnit unit) throws java.lang.InterruptedException, java.util.concurrent.ExecutionException, java.util.concurrent.TimeoutException
Description copied from class:AbstractFuture
The default
AbstractFuture
implementation throwsInterruptedException
if the current thread is interrupted before or during the call, even if the value is already available.- Specified by:
get
in interfacejava.util.concurrent.Future<V>
- Overrides:
get
in classAbstractFuture<V>
- Throws:
java.lang.InterruptedException
- if the current thread was interrupted before or during the call (optional but recommended).java.util.concurrent.ExecutionException
java.util.concurrent.TimeoutException
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isDone
public final boolean isDone()
- Specified by:
isDone
in interfacejava.util.concurrent.Future<V>
- Overrides:
isDone
in classAbstractFuture<V>
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isCancelled
public final boolean isCancelled()
- Specified by:
isCancelled
in interfacejava.util.concurrent.Future<V>
- Overrides:
isCancelled
in classAbstractFuture<V>
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addListener
public final void addListener(java.lang.Runnable listener, java.util.concurrent.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: 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>
- Overrides:
addListener
in classAbstractFuture<V>
- Parameters:
listener
- the listener to run when the computation is completeexecutor
- the executor to run the listener in
- The listener may be executed by the caller of
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cancel
public final boolean cancel(boolean mayInterruptIfRunning)
Description copied from class:AbstractFuture
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.- Specified by:
cancel
in interfacejava.util.concurrent.Future<V>
- Overrides:
cancel
in classAbstractFuture<V>
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