CompletionService

public interface CompletionService
Known Indirect Subclasses

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 I/O, 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 Executor to actually execute the tasks, in which case the CompletionService only manages an internal completion queue. The ExecutorCompletionService class provides an implementation of this approach.

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

Public Method Summary

abstract Future<V>
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.
abstract Future<V>
poll()
Retrieves and removes the Future representing the next completed task, or null if none are present.
abstract Future<V>
submit(Runnable task, V result)
Submits a Runnable task for execution and returns a Future representing that task.
abstract Future<V>
submit(Callable<V> task)
Submits a value-returning task for execution and returns a Future representing the pending results of the task.
abstract Future<V>