Stream, spliterator, supplier and size

[Remi Forax]

Brian explains why there is methods in Streams that takes a Supplier and 
the flags in a previous mail
(I'm too lazy to find it now).
   <T> Stream<T> stream(Supplier<Spliterator<T>> supplier, int flags)

I've trouble to understand why we need to expose two semantics to our 
poor users,
I think it's better to decide whenever (1) the spliterator is created 
when collection.stream() is called
or (2) the spliterator is created when a terminal operation like 
stream.forEach is called.

It has severe implications on the way the pipeline works under the hood 
because the pipeline ops may relies on the size of the collection which 
may be different if the collection is mutated between the creation of 
the stream and the call to the terminal operation.

cheers,
Rémi