Package com.google.common.util.concurrent

Class ForwardingExecutorService

java.lang.Object

com.google.common.collect.ForwardingObject

com.google.common.util.concurrent.ForwardingExecutorService

All Implemented Interfaces:

Executor, ExecutorService

Direct Known Subclasses:

ForwardingListeningExecutorService

@CanIgnoreReturnValue
@GwtIncompatible
public abstract class ForwardingExecutorService
extends ForwardingObject
implements ExecutorService

An executor service which forwards all its method calls to another executor service. Subclasses should override one or more methods to modify the behavior of the backing executor service as desired per the decorator pattern.

Since:

10.0

Author:

Kurt Alfred Kluever

Constructor Summary

Constructors

Modifier	Constructor	Description
protected	ForwardingExecutorService()	Constructor for use by subclasses.

Method Summary

Modifier and Type	Method	Description
boolean	awaitTermination(long timeout, TimeUnit unit)	Blocks until all tasks have completed execution after a shutdown request, or the timeout occurs, or the current thread is interrupted, whichever happens first.
protected abstract ExecutorService	delegate()	Returns the backing delegate instance that methods are forwarded to.
void	execute(Runnable command)	Executes the given command at some time in the future.
<T extends @Nullable Object> List<Future<T>>	invokeAll(Collection<? extends Callable<T>> tasks)	Executes the given tasks, returning a list of Futures holding their status and results when all complete.
<T extends @Nullable Object> List<Future<T>>	invokeAll(Collection<? extends Callable<T>> tasks, long timeout, TimeUnit unit)	Executes the given tasks, returning a list of Futures holding their status and results when all complete or the timeout expires, whichever happens first.
<T extends @Nullable Object> T	invokeAny(Collection<? extends Callable<T>> tasks)	Executes the given tasks, returning the result of one that has completed successfully (i.e., without throwing an exception), if any do.
<T extends @Nullable Object> T	invokeAny(Collection<? extends Callable<T>> tasks, long timeout, TimeUnit unit)	Executes the given tasks, returning the result of one that has completed successfully (i.e., without throwing an exception), if any do before the given timeout elapses.
boolean	isShutdown()	Returns true if this executor has been shut down.
boolean	isTerminated()	Returns true if all tasks have completed following shut down.
void	shutdown()	Initiates an orderly shutdown in which previously submitted tasks are executed, but no new tasks will be accepted.
List<Runnable>	shutdownNow()	Attempts to stop all actively executing tasks, halts the processing of waiting tasks, and returns a list of the tasks that were awaiting execution.
Future<?>	submit(Runnable task)	Submits a Runnable task for execution and returns a Future representing that task.
<T extends @Nullable Object> Future<T>	submit(Runnable task, T result)	Submits a Runnable task for execution and returns a Future representing that task.
<T extends @Nullable Object> Future<T>	submit(Callable<T> task)	Submits a value-returning task for execution and returns a Future representing the pending results of the task.

Methods inherited from class com.google.common.collect.ForwardingObject

toString

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait

Constructor Detail

ForwardingExecutorService

protected ForwardingExecutorService()

Constructor for use by subclasses.

Method Detail

delegate

protected abstract ExecutorService delegate()

Description copied from class: ForwardingObject

Returns the backing delegate instance that methods are forwarded to. Abstract subclasses generally override this method with an abstract method that has a more specific return type, such as ForwardingSet.delegate(). Concrete subclasses override this method to supply the instance being decorated.

Specified by:

delegate in class ForwardingObject

awaitTermination

public boolean awaitTermination(long timeout,
                                TimeUnit unit)
                         throws InterruptedException

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

Blocks until all tasks have completed execution after a shutdown request, or the timeout occurs, or the current thread is interrupted, whichever happens first.

Specified by:

awaitTermination in interface ExecutorService

Parameters:

timeout - the maximum time to wait

unit - the time unit of the timeout argument

Returns:

true if this executor terminated and false if the timeout elapsed before termination

Throws:

InterruptedException - if interrupted while waiting

invokeAll

public <T extends @Nullable Object> List<Future<T>> invokeAll(Collection<? extends Callable<T>> tasks)
                                                       throws InterruptedException

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

Executes the given tasks, returning a list of Futures holding their status and results when all complete. Future.isDone() is true for each element of the returned list. Note that a completed task could have terminated either normally or by throwing an exception. The results of this method are undefined if the given collection is modified while this operation is in progress.

Specified by:

invokeAll in interface ExecutorService

Type Parameters:

T - the type of the values returned from the tasks

Parameters:

tasks - the collection of tasks

Returns:

a list of Futures representing the tasks, in the same sequential order as produced by the iterator for the given task list, each of which has completed

Throws:

InterruptedException - if interrupted while waiting, in which case unfinished tasks are cancelled

invokeAll

public <T extends @Nullable Object> List<Future<T>> invokeAll(Collection<? extends Callable<T>> tasks,
                                                              long timeout,
                                                              TimeUnit unit)
                                                       throws InterruptedException

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

Executes the given tasks, returning a list of Futures holding their status and results when all complete or the timeout expires, whichever happens first. Future.isDone() is true for each element of the returned list. Upon return, tasks that have not completed are cancelled. Note that a completed task could have terminated either normally or by throwing an exception. The results of this method are undefined if the given collection is modified while this operation is in progress.

Specified by:

invokeAll in interface ExecutorService

Type Parameters:

T - the type of the values returned from the tasks

Parameters:

tasks - the collection of tasks

timeout - the maximum time to wait

unit - the time unit of the timeout argument

Returns:

a list of Futures representing the tasks, in the same sequential order as produced by the iterator for the given task list. If the operation did not time out, each task will have completed. If it did time out, some of these tasks will not have completed.

Throws:

InterruptedException - if interrupted while waiting, in which case unfinished tasks are cancelled

invokeAny

public <T extends @Nullable Object> T invokeAny(Collection<? extends Callable<T>> tasks)
                                         throws InterruptedException,
                                                ExecutionException

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

Executes the given tasks, returning the result of one that has completed successfully (i.e., without throwing an exception), if any do. Upon normal or exceptional return, tasks that have not completed are cancelled. The results of this method are undefined if the given collection is modified while this operation is in progress.

Specified by:

invokeAny in interface ExecutorService

Type Parameters:

T - the type of the values returned from the tasks

Parameters:

tasks - the collection of tasks

Returns:

the result returned by one of the tasks

Throws:

InterruptedException - if interrupted while waiting

ExecutionException - if no task successfully completes

invokeAny

public <T extends @Nullable Object> T invokeAny(Collection<? extends Callable<T>> tasks,
                                                long timeout,
                                                TimeUnit unit)
                                         throws InterruptedException,
                                                ExecutionException,
                                                TimeoutException

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

Executes the given tasks, returning the result of one that has completed successfully (i.e., without throwing an exception), if any do before the given timeout elapses. Upon normal or exceptional return, tasks that have not completed are cancelled. The results of this method are undefined if the given collection is modified while this operation is in progress.

Specified by:

invokeAny in interface ExecutorService

Type Parameters:

T - the type of the values returned from the tasks

Parameters:

tasks - the collection of tasks

timeout - the maximum time to wait

unit - the time unit of the timeout argument

Returns:

the result returned by one of the tasks

Throws:

InterruptedException - if interrupted while waiting

ExecutionException - if no task successfully completes

TimeoutException - if the given timeout elapses before any task successfully completes

isShutdown

public boolean isShutdown()

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

Returns true if this executor has been shut down.

Specified by:

isShutdown in interface ExecutorService

Returns:

true if this executor has been shut down

isTerminated

public boolean isTerminated()

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

Returns true if all tasks have completed following shut down. Note that isTerminated is never true unless either shutdown or shutdownNow was called first.

Specified by:

isTerminated in interface ExecutorService

Returns:

true if all tasks have completed following shut down

shutdown

public void shutdown()

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

Initiates an orderly shutdown in which previously submitted tasks are executed, but no new tasks will be accepted. Invocation has no additional effect if already shut down.

This method does not wait for previously submitted tasks to complete execution. Use awaitTermination to do that.

Specified by:

shutdown in interface ExecutorService

shutdownNow

public List<Runnable> shutdownNow()

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

Attempts to stop all actively executing tasks, halts the processing of waiting tasks, and returns a list of the tasks that were awaiting execution.

This method does not wait for actively executing tasks to terminate. Use awaitTermination to do that.

There are no guarantees beyond best-effort attempts to stop processing actively executing tasks. For example, typical implementations will cancel via Thread.interrupt(), so any task that fails to respond to interrupts may never terminate.

Specified by:

shutdownNow in interface ExecutorService

Returns:

list of tasks that never commenced execution

execute

public void execute(Runnable command)

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

Executes the given command at some time in the future. The command may execute in a new thread, in a pooled thread, or in the calling thread, at the discretion of the Executor implementation.

Specified by:

execute in interface Executor

Parameters:

command - the runnable task

submit

public <T extends @Nullable Object> Future<T> submit(Callable<T> task)

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

Submits a value-returning task for execution and returns a Future representing the pending results of the task. The Future's get method will return the task's result upon successful completion.

If you would like to immediately block waiting for a task, you can use constructions of the form result = exec.submit(aCallable).get();

Note: The Executors class includes a set of methods that can convert some other common closure-like objects, for example, PrivilegedAction to Callable form so they can be submitted.

Specified by:

submit in interface ExecutorService

Type Parameters:

T - the type of the task's result

Parameters:

task - the task to submit

Returns:

a Future representing pending completion of the task

submit

public Future<?> submit(Runnable task)

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

Submits a Runnable task for execution and returns a Future representing that task. The Future's get method will return null upon successful completion.

Specified by:

submit in interface ExecutorService

Parameters:

task - the task to submit

Returns:

a Future representing pending completion of the task

submit

public <T extends @Nullable Object> Future<T> submit(Runnable task,
                                                     T result)

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

Submits a Runnable task for execution and returns a Future representing that task. The Future's get method will return the given result upon successful completion.

Specified by:

submit in interface ExecutorService

Type Parameters:

T - the type of the result

Parameters:

task - the task to submit

result - the result to return

Returns:

a Future representing pending completion of the task