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 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.
Retrieves and removes the Future representing the next
completed task or null 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 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.
Submits a Runnable task for execution and returns a Future
representing that task.Upon completion,
this task may be taken or polled.
Retrieves and removes the Future representing the next
completed task, waiting if none are yet present.