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java.util.concurrent
interface CompletionService

All Known Implementing Classes:
ExecutorCompletionService

public interface CompletionService

A service that decouples the production of new asynchronous tasks from the consumption of the results of completed tasks. Producers submit tasks for execution. Consumers take completed tasks and process their results in the order they complete. A CompletionService can for example be used to manage asynchronous IO, in which tasks that perform reads are submitted in one part of a program or system, and then acted upon in a different part of the program when the reads complete, possibly in a different order than they were requested.

Typically, a CompletionService relies on a separate {@link Executor} to actually execute the tasks, in which case the CompletionService only manages an internal completion queue. The {@link ExecutorCompletionService} class provides an implementation of this approach.

Memory consistency effects: Actions in a thread prior to submitting a task to a {@code CompletionService} happen-before actions taken by that task, which in turn happen-before actions following a successful return from the corresponding {@code take()}.


Method Summary
 Future

          Retrieves and removes the Future representing the next completed task or null if none are present.
 Future
poll(long timeout, TimeUnit unit)

          Retrieves and removes the Future representing the next completed task, waiting if necessary up to the specified wait time if none are yet present.
 Future

          Submits a value-returning task for execution and returns a Future representing the pending results of the task.
 Future
submit(Runnable task, Object result)

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

          Retrieves and removes the Future representing the next completed task, waiting if none are yet present.
 

Method Detail

poll

public Future poll()
Retrieves and removes the Future representing the next completed task or null if none are present.

Returns:
the Future representing the next completed task, or null if none are present

poll

public Future poll(long timeout,
                   TimeUnit unit)
            throws InterruptedException
Retrieves and removes the Future representing the next completed task, waiting if necessary up to the specified wait time if none are yet present.

Parameters:
timeout - how long to wait before giving up, in units of unit
unit - a TimeUnit determining how to interpret the timeout parameter
Returns:
the Future representing the next completed task or null if the specified waiting time elapses before one is present
Throws:
InterruptedException - if interrupted while waiting

submit

public Future submit(Callable task)
Submits a value-returning task for execution and returns a Future representing the pending results of the task. Upon completion, this task may be taken or polled.

Parameters:
task - the task to submit
Returns:
a Future representing pending completion of the task

submit

public Future submit(Runnable task,
                     Object result)
Submits a Runnable task for execution and returns a Future representing that task. Upon completion, this task may be taken or polled.

Parameters:
task - the task to submit
result - the result to return upon successful completion
Returns:
a Future representing pending completion of the task, and whose get() method will return the given result value upon completion

take

public Future take()
            throws InterruptedException
Retrieves and removes the Future representing the next completed task, waiting if none are yet present.

Returns:
the Future representing the next completed task
Throws:
InterruptedException - if interrupted while waiting


This documentation differs from the official API. Jadeite adds extra features to the API including: variable font sizes, constructions examples, placeholders for classes and methods, and auto-generated “See Also” links. Additionally it is missing some items found in standard Javadoc documentation, including: generics type information, “Deprecated” tags and comments, “See Also” links, along with other minor differences. Please send any questions or feedback to bam@cs.cmu.edu.
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Copyright 2008 Sun Microsystems, Inc. All rights reserved. Use is subject to license terms. Also see the documentation redistribution policy.
The official Sun™ documentation can be found here at http://java.sun.com/javase/6/docs/api/.