CompletionStage instead of Future for Submission#cancel return type?

[Sebastien Deleuze]

While reviewing ADBA API, I noticed that Submission#cancel returns Future
[1], which in practice is mostly usable in a blocking way since get() is
blocking, checking regularly isDone() is not convenient at all, and
unlike CompletionStage it does not provide a way to register a complete
callback.

Is there any specific reason why CompletionStage<Boolean> can't be used
there as return type? In addition to providing a non-blocking API, that
would be also more consistent.

I am also not sure about Submission#getCompletionStage method name. Maybe
something like Submission#getResult would be more clear than just naming it
against the return type, especially if there are 2 methods returning
CompletionStage
like in my proposal.

Any thoughts?

[1]
http://cr.openjdk.java.net/~lancea/apidoc/java/sql2/Submission.html#cancel--