- Type Parameters:
V
- the type of values the tasks of this service produce and consume
- All Known Implementing Classes:
ExecutorCompletionService
public interface CompletionService<V>
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()
.
- Since:
- 1.5
-
Method Summary
Modifier and TypeMethodDescriptionpoll()
Retrieves and removes the Future representing the next completed task, ornull
if none are present.Retrieves and removes the Future representing the next completed task, waiting if necessary up to the specified wait time if none are yet present.Submits a Runnable task for execution and returns a Future representing that task.Submits a value-returning task for execution and returns a Future representing the pending results of the task.take()
Retrieves and removes the Future representing the next completed task, waiting if none are yet present.
-
Method Details
-
submit
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
- Throws:
RejectedExecutionException
- if the task cannot be scheduled for executionNullPointerException
- if the task is null
-
submit
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 submitresult
- 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 - Throws:
RejectedExecutionException
- if the task cannot be scheduled for executionNullPointerException
- if the task is null
-
take
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
-
poll
-
poll
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 ofunit
unit
- aTimeUnit
determining how to interpret thetimeout
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
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