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java.util.concurrent
Class AbstractExecutorService

java.lang.Object
  java.util.concurrent.AbstractExecutorService

All Implemented Interfaces:

Executor, ExecutorService

Direct Known Subclasses:

ForkJoinPool, ThreadPoolExecutor

public abstract class AbstractExecutorService
extends Object
implements ExecutorService

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.
 }
 

Since:

1.5

Constructor and Description

AbstractExecutorService()

Method Summary

Modifier and Type	Method and Description
<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.
protected <T> RunnableFuture<T>	newTaskFor(Callable<T> callable) Returns a RunnableFuture for the given callable task.
protected <T> RunnableFuture<T>	newTaskFor(Runnable runnable, T value) Returns a RunnableFuture for the given runnable and default value.
<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.
Future<?>	submit(Runnable task) Submits a Runnable task for execution and returns a Future representing that task.
<T> Future<T>	submit(Runnable task, T result) Submits a Runnable task for execution and returns a Future representing that task.

Methods inherited from class java.lang.Object

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

Methods inherited from interface java.util.concurrent.ExecutorService

awaitTermination, isShutdown, isTerminated, shutdown, shutdownNow

Methods inherited from interface java.util.concurrent.Executor

execute

Constructor Detail

AbstractExecutorService

public AbstractExecutorService()

Method Detail

newTaskFor

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

Returns a RunnableFuture for the given runnable and default value.

Parameters:

runnable - the runnable task being wrapped

value - the default value for the returned future

Returns:

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.

Since:

1.6

newTaskFor

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

Returns a RunnableFuture for the given callable task.

Parameters:

callable - the callable task being wrapped

Returns:

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.

Since:

1.6

submit

public Future<?> submit(Runnable task)

Description copied from interface: 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

Throws:

RejectedExecutionException - if the task cannot be scheduled for execution

NullPointerException - if the task is null

submit

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

Description copied from interface: 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

Parameters:

task - the task to submit

result - the result to return

Returns:

a Future representing pending completion of the task

Throws:

RejectedExecutionException - if the task cannot be scheduled for execution

NullPointerException - if the task is null

submit

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

Description copied from interface: 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

Parameters:

task - the task to submit

Returns:

a Future representing pending completion of the task

Throws:

RejectedExecutionException - if the task cannot be scheduled for execution

NullPointerException - if the task is null

invokeAny

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

Description copied from interface: 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

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

Description copied from interface: 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

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

invokeAll

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

Description copied from interface: 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

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

Description copied from interface: 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

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