"Cancelable" streams

[Joe Bowbeer]

Questions:

How often is the BooleanSupplier called?

Can one implement a BooleanSupplier that depended on the number of elements
generated?  (Or would you just use a lazy range method instead?)

Doesn't cancellation occur as soon as the supplier returns false?  If so,
what's the advantage of an onCancel method?  Or is it possible for the
stream to be canceled by some other means?



> The way this works is that it polls the supplied BooleanSupplier to ask
> "should we cancel now."  Once canceled, it acts as a gate shutting; no more
> elements are sent downstream, so downstream processing completes as if the
> stream were truncated.  When cancelation occurs, it calls the onCancel
> Runnable so that the client can have a way to know that the pipeline
> completed due to cancelation rather than normal completion.


On Sat, Dec 8, 2012 at 11:27 AM, Brian Goetz <brian.goetz at oracle.com> wrote:

> The way this works is that it polls the supplied BooleanSupplier to ask
> "should we cancel now."  Once canceled, it acts as a gate shutting; no more
> elements are sent downstream, so downstream processing completes as if the
> stream were truncated.  When cancelation occurs, it calls the onCancel
> Runnable so that the client can have a way to know that the pipeline
> completed due to cancelation rather than normal completion.
>