Interface CompletionService<V>
- 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 Type | Method | Description |
---|---|---|
Future<V> | poll() | Retrieves and removes the Future representing the next completed task, or |
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. |
Future<V> | submit(Runnable task,
V result) | Submits a Runnable task for execution and returns a Future representing that task. |
Future<V> | submit(Callable<V> task) | Submits a value-returning task for execution and returns a Future representing the pending results of the task. |
Future<V> | take() | Retrieves and removes the Future representing the next completed task, waiting if none are yet present. |
Method Detail
submit
Future<V> submit(Callable<V> 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
- Throws:
-
RejectedExecutionException
- if the task cannot be scheduled for execution -
NullPointerException
- if the task is null
submit
Future<V> submit(Runnable task, V 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 - Throws:
-
RejectedExecutionException
- if the task cannot be scheduled for execution -
NullPointerException
- if the task is null
take
Future<V> 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
poll
Future<V> 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
Future<V> 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 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