[concurrency-interest] No *Task counterpart of CompletableFuture?

Doug Lea dl at cs.oswego.edu
Tue Feb 11 14:46:32 EST 2014

On 02/10/2014 07:24 PM, Tomas Mikula wrote:
> Hi,
> I really like the addition of the CompletionStage interface in 1.8.
> However, there is just one implementation of it and that is
> CompletableFuture. I am missing a task counterpart of it, i.e.
> something that is both a Future and a CompletionStage, but is
> completed by a computation (i.e. takes a Callable constructor argument
> or has a protected abstract compute() method).

There are instead (four) static methods that accept functions and return
a CompletableFuture that is complete after they run. For example
supplyAsync is pasted below. Do you have usages in mind where
you'd need something different?

      * Returns a new CompletableFuture that is asynchronously completed
      * by a task running in the given executor with the value obtained
      * by calling the given Supplier.
      * @param supplier a function returning the value to be used
      * to complete the returned CompletableFuture
      * @param executor the executor to use for asynchronous execution
      * @param <U> the function's return type
      * @return the new CompletableFuture
     public static <U> CompletableFuture<U> supplyAsync(Supplier<U> supplier,
                                                        Executor executor)

> I imagine a hierarchy like this:
> interface CompletionFuture<T> extends Future<T>, CompletionStage<T> {}
> class CompletableFuture<T> implements CompletionFuture<T> {...}
> class CompletionFutureTask<T> implements CompletionFuture<T> {
>      public CompletionFutureTask(Callable<T> callable) {...}
>      // or
>      protected abstract T compute();
> }
> Is there a reason why this is missing? Is there a plan to add this?
> Thanks,
> Tomas
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