Package com.google.common.util.concurrent

Class ListenableFutureTask<V>

java.lang.Object

java.util.concurrent.FutureTask<V>

com.google.common.util.concurrent.ListenableFutureTask<V>

All Implemented Interfaces:

ListenableFuture<V>, Runnable, Future<V>, RunnableFuture<V>

@GwtIncompatible
public class ListenableFutureTask<V>
extends FutureTask<V>
implements ListenableFuture<V>

A 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

Author:

Sven Mawson

Method Summary

Modifier and Type	Method	Description
void	addListener(Runnable listener, Executor exec)	Registers a listener to be run on the given executor.
static <V> ListenableFutureTask<V>	create(Runnable runnable, @Nullable 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.
static <V> ListenableFutureTask<V>	create(Callable<V> callable)	Creates a ListenableFutureTask that will upon running, execute the given Callable.
protected void	done()	Internal implementation detail used to invoke the listeners.
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.

Methods inherited from class java.util.concurrent.FutureTask

cancel, get, isCancelled, isDone, run, runAndReset, set, setException, 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, get, isCancelled, isDone

Method Detail

create

public static <V> ListenableFutureTask<V> create(Callable<V> callable)

Creates a ListenableFutureTask that will upon running, execute the given Callable.

Parameters:

callable - the callable task

Since:

10.0

create

public static <V> ListenableFutureTask<V> create(Runnable runnable,
                                                 @Nullable 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.

Parameters:

runnable - the runnable task

result - 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

public void addListener(Runnable listener,
                        Executor exec)

Description copied from interface: ListenableFuture

Registers a listener to be run on the given executor. The listener will run when the 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: If your listener is lightweight -- and will not cause stack overflow by completing more futures or adding more directExecutor() listeners inline -- consider MoreExecutors.directExecutor(). Otherwise, avoid it: See the warnings on the docs for directExecutor.

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.

Guava implementations of ListenableFuture promptly release references to listeners after executing them.

Specified by:

addListener in interface ListenableFuture<V>

Parameters:

listener - the listener to run when the computation is complete

exec - the executor to run the listener in

get

@CanIgnoreReturnValue
public V get(long timeout,
             TimeUnit unit)
      throws TimeoutException,
             InterruptedException,
             ExecutionException

Description copied from interface: java.util.concurrent.Future

Waits if necessary for at most the given time for the computation to complete, and then retrieves its result, if available.

Specified by:

get in interface Future<V>

Overrides:

get in class FutureTask<V>

Parameters:

timeout - the maximum time to wait

unit - the time unit of the timeout argument

Returns:

the computed result

Throws:

TimeoutException - if the wait timed out

InterruptedException - if the current thread was interrupted while waiting

ExecutionException - if the computation threw an exception

done

protected void done()

Internal implementation detail used to invoke the listeners.

Overrides:

done in class FutureTask<V>