There is no value in making users remember which stream methods are
null-hostile and which are null-tolerant; this is just more accidental
complexity.
I think that ship has sailed a long ago.
Some collectors are null hostile, some are not.
You can make a point that a Collector is technically not the Stream API per se.
Yes, and this is no mere "technical argument". A Collector is a
collection of behaviors, governed by its own spec. The behaviors passed
to stream operations, whether they be lambdas passed by the user
(`.map(x -> x.hopeXIsntNull())`) or collector objects or comparators,
are under the control of the user, and it is the user's responsibility
to pass behaviors which are compatible with the data domain -- which the
user knows and the streams implementation cannot know.
Because of that, i don't think we even have the choice of the semantics for
Stream.toList(), it has to be the same as stream.collect(Collectors.toList()).
This doesn't remotely follow. (And, if it did, I would likely not even
support this RFE.) The spec of Collectors::toList was crafted to
disavow pretty much anything other than List-hood, in part in
anticipation of this addition.
But it can not be immutable too, for the same reason.
Nope. The spec of toList() very clearly says: no guarantees as to the
type, mutability, serializability, etc etc of the returned list. That
doesn't mean that every method returning a List added to the JDK after
Collectors::toList must similarly disavow all such guarantees.
(In fact, we would be entirely justified to change the behavior of
Collectors::toList tomorrow, to match the proposed Stream::toList; the
spec was crafted to preserve this option. We probably won't, because
there are too many programmers who refuse to read the specification, and
have baked in the assumption that it returns an ArrayList, and this
would likely just be picking a fight for little good reason, regardless
of who is right.)
Please, can we stop having this same tired "I hate nulls, let's find a
new way to punish people who like them" discussion for every single
feature?
