AbstractExecutorService

public abstract class AbstractExecutorService
extends Object implements ExecutorService

java.lang.Object
   ↳ java.util.concurrent.AbstractExecutorService
ForkJoinPool An ExecutorService for running ForkJoinTasks. 
ThreadPoolExecutor An ExecutorService that executes each submitted task using one of possibly several pooled threads, normally configured using Executors factory methods. 
ScheduledThreadPoolExecutor A ThreadPoolExecutor that can additionally schedule commands to run after a given delay, or to execute periodically. 


Provides default implementations of ExecutorService execution methods. This class implements the submit, invokeAny and invokeAll methods using a RunnableFuture returned by newTaskFor, which defaults to the FutureTask class provided in this package. For example, the implementation of submit(Runnable) creates an associated RunnableFuture that is executed and returned. Subclasses may override the newTaskFor methods to return RunnableFuture implementations other than FutureTask.

Extension example. Here is a sketch of a class that customizes ThreadPoolExecutor to use a CustomTask class instead of the default FutureTask:

 public class CustomThreadPoolExecutor extends ThreadPoolExecutor {

   static class CustomTask<V> implements RunnableFuture<V> { ... }

   protected <V> RunnableFuture<V> newTaskFor(Callable<V> c) {
       return new CustomTask<V>(c);
   }
   protected <V> RunnableFuture<V> newTaskFor(Runnable r, V v) {
       return new CustomTask<V>(r, v);
   }
   // ... add constructors, etc.
 }

Summary

Public constructors

AbstractExecutorService()

Constructor for subclasses to call.

Public methods

<T> 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> 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> 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> 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.

<T> Future<T> submit(Callable<T> task)

Submits a value-returning task for execution and returns a Future representing the pending results of the task.

<T> Future<T> submit(Runnable task, T result)

Submits a Runnable task for execution and returns a Future representing that task.

Future<?> submit(Runnable task)

Submits a Runnable task for execution and returns a Future representing that task.

Protected methods

<T> RunnableFuture<T> newTaskFor(Runnable runnable, T value)

Returns a RunnableFuture for the given runnable and default value.

<T> RunnableFuture<T> newTaskFor(Callable<T> callable)

Returns a RunnableFuture for the given callable task.

Inherited methods

Object clone()

Creates and returns a copy of this object.

boolean equals(Object obj)

Indicates whether some other object is "equal to" this one.

void finalize()

Called by the garbage collector on an object when garbage collection determines that there are no more references to the object.

final Class<?> getClass()

Returns the runtime class of this Object.

int hashCode()

Returns a hash code value for the object.

final void notify()

Wakes up a single thread that is waiting on this object's monitor.

final void notifyAll()

Wakes up all threads that are waiting on this object's monitor.

String toString()

Returns a string representation of the object.

final void wait(long timeoutMillis, int nanos)

Causes the current thread to wait until it is awakened, typically by being notified or interrupted, or until a certain amount of real time has elapsed.

final void wait(long timeoutMillis)

Causes the current thread to wait until it is awakened, typically by being notified or interrupted, or until a certain amount of real time has elapsed.

final void wait()

Causes the current thread to wait until it is awakened, typically by being notified or interrupted.

abstract 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.

default void close()

Initiates an orderly shutdown in which previously submitted tasks are executed, but no new tasks will be accepted.

abstract <T> 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.

abstract <T> 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.

abstract <T> 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.

abstract <T> 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.

abstract boolean isShutdown()

Returns true if this executor has been shut down.

abstract boolean isTerminated()

Returns true if all tasks have completed following shut down.

abstract void shutdown()

Initiates an orderly shutdown in which previously submitted tasks are executed, but no new tasks will be accepted.

abstract 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.

abstract Future<?> submit(Runnable task)

Submits a Runnable task for execution and returns a Future representing that task.

abstract <T> Future<T> submit(Callable<T> task)

Submits a value-returning task for execution and returns a Future representing the pending results of the task.

abstract <T> Future<T> submit(Runnable task, T result)

Submits a Runnable task for execution and returns a Future representing that task.

abstract void close()

Closes this resource, relinquishing any underlying resources.

abstract void execute(Runnable command)

Executes the given command at some time in the future.

Public constructors

AbstractExecutorService

Added in API level 1
public AbstractExecutorService ()

Constructor for subclasses to call.

Public methods

invokeAll

Added in API level 1
public 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. 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.

Parameters
tasks Collection: the collection of tasks

Returns
List<Future<T>> 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

invokeAll

Added in API level 1
public 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. 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.

Parameters
tasks Collection: the collection of tasks

timeout long: the maximum time to wait

unit TimeUnit: the time unit of the timeout argument

Returns
List<Future<T>> 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.

invokeAny

Added in API level 1
public 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. 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.

Parameters
tasks Collection: the collection of tasks

Returns
T the result returned by one of the tasks

invokeAny

Added in API level 1
public 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. 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.

Parameters
tasks Collection: the collection of tasks

timeout long: the maximum time to wait

unit TimeUnit: the time unit of the timeout argument

Returns
T the result returned by one of the tasks

submit

Added in API level 1
public Future<T> submit (Callable<T> task)

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.

Parameters
task Callable: the task to submit

Returns
Future<T> a Future representing pending completion of the task

submit

Added in API level 1
public Future<T> submit (Runnable task, 
                T result)

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.

Parameters
task Runnable: the task to submit

result T: the result to return

Returns
Future<T> a Future representing pending completion of the task

submit

Added in API level 1
public Future<?> submit (Runnable task)

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

Parameters
task Runnable: the task to submit

Returns
Future<?> a Future representing pending completion of the task

Protected methods

newTaskFor

Added in API level 9
protected RunnableFuture<T> newTaskFor (Runnable runnable, 
                T value)

Returns a RunnableFuture for the given runnable and default value.

Parameters
runnable Runnable: the runnable task being wrapped

value T: the default value for the returned future

Returns
RunnableFuture<T> a RunnableFuture which, when run, will run the underlying runnable and which, as a Future, will yield the given value as its result and provide for cancellation of the underlying task

newTaskFor

Added in API level 9
protected RunnableFuture<T> newTaskFor (Callable<T> callable)

Returns a RunnableFuture for the given callable task.

Parameters
callable Callable: the callable task being wrapped

Returns
RunnableFuture<T> a RunnableFuture which, when run, will call the underlying callable and which, as a Future, will yield the callable's result as its result and provide for cancellation of the underlying task