java.util.concurrent

Class AbstractExecutorService

Implemented Interfaces:
Executor, ExecutorService
Known Direct Subclasses:
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

Method Summary

Future submit(Callable task)
Submits a value-returning task for execution and returns a Future representing the pending results of the task.
Future submit(Runnable task, T result)
Submits a Runnable task for execution and returns a Future representing that task.
List> invokeAll(Callable> tasks)
Executes the given tasks, returning a list of Futures holding their status and results when all complete.
List> invokeAll(Callable> 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.
protected
RunnableFuture newTaskFor(Callable callable)
Returns a RunnableFuture for the given callable task.
protected
RunnableFuture newTaskFor(Runnable runnable, T value)
Returns a RunnableFuture for the given runnable and default value.
T invokeAny(Callable> tasks)
Executes the given tasks, returning the result of one that has completed successfully (i.e., without throwing an exception), if any do.
T invokeAny(Callable> 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.
Future
submit(Runnable task)
Submits a Runnable task for execution and returns a Future representing that task.

Methods inherited from class java.lang.Object

clone, equals, extends Object> getClass, finalize, hashCode, notify, notifyAll, toString, wait, wait, wait

Method Details

Future submit

public  Future submit(Callable 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.

Specified by:
Future 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

Future submit

public  Future 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.
Specified by:
Future 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

List> invokeAll

public  List> invokeAll(Callable> tasks)
            throws InterruptedException
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:
List> 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.
NullPointerException - if tasks or any of its elements are null
RejectedExecutionException - if any task cannot be scheduled for execution

List> invokeAll

public  List> invokeAll(Callable> tasks,
                                     long timeout,
                                     TimeUnit unit)
            throws InterruptedException
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:
List> 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
NullPointerException - if tasks, any of its elements, or unit are null
RejectedExecutionException - if any task cannot be scheduled for execution

RunnableFuture newTaskFor

protected  RunnableFuture newTaskFor(Callable 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

RunnableFuture newTaskFor

protected  RunnableFuture 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

T invokeAny

public  T invokeAny(Callable> tasks)
            throws InterruptedException,
                   ExecutionException
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:
T 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
NullPointerException - if tasks or any of its elements are null
IllegalArgumentException - if tasks is empty
ExecutionException - if no task successfully completes
RejectedExecutionException - if tasks cannot be scheduled for execution

T invokeAny

public  T invokeAny(Callable> tasks,
                       long timeout,
                       TimeUnit unit)
            throws InterruptedException,
                   ExecutionException,
                   TimeoutException
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:
T 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
NullPointerException - if tasks, any of its elements, or unit are null
TimeoutException - if the given timeout elapses before any task successfully completes
ExecutionException - if no task successfully completes
RejectedExecutionException - if tasks cannot be scheduled for execution

submit

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.
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