Interface CompletionService<V>
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- 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. Producerssubmittasks for execution. Consumerstakecompleted tasks and process their results in the order they complete. ACompletionServicecan 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
CompletionServicerelies on a separateExecutorto actually execute the tasks, in which case theCompletionServiceonly manages an internal completion queue. TheExecutorCompletionServiceclass provides an implementation of this approach.Memory consistency effects: Actions in a thread prior to submitting a task to a
CompletionServicehappen-before actions taken by that task, which in turn happen-before actions following a successful return from the correspondingtake().
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Method Summary
All Methods Instance Methods Abstract Methods Modifier and Type Method and Description Future<V>poll()Retrieves and removes the Future representing the next completed task, ornullif none are present.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(Callable<V> task)Submits a value-returning task for execution and returns a Future representing the pending results of the task.Future<V>submit(Runnable task, V result)Submits a Runnable task for execution and returns a Future representing that task.Future<V>take()Retrieves and removes the Future representing the next completed task, waiting if none are yet present.
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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:
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task- the task to submit - Returns:
- a Future representing pending completion of the task
- Throws:
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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:
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task- the task to submit -
result- the result to return upon successful completion - Returns:
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a Future representing pending completion of the task, and whose
get()method will return the given result value upon completion - Throws:
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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:
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InterruptedException- if interrupted while waiting
poll
Future<V> poll()
Retrieves and removes the Future representing the next completed task, ornullif none are present.- Returns:
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the Future representing the next completed task, or
nullif 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:
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timeout- how long to wait before giving up, in units ofunit -
unit- aTimeUnitdetermining how to interpret thetimeoutparameter - Returns:
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the Future representing the next completed task or
nullif the specified waiting time elapses before one is present - Throws:
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InterruptedException- if interrupted while waiting
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