Discussion: Introduce a `Stream.reject` method, the opposite of `Stream.filter`

[Paul Sandoz]

Hi Jason,

One of the rationals for adding “Predicate.not" is to avoid adding another stream operation, such as “reject" or “filterNot", and instead one can use "filter(not(String::isEmpty))” rather than “filter(s -> !s.isEmpty())” if so desired. (This was the reason why i did not close down the issue, and sat on it, and thankfully Jim took action.)

We are trying to avoid adding “overloaded" forms of the same kind of operation, such as in this case, or filtering classes, or filtering values etc.

Hth,
Paul.

> On May 18, 2018, at 11:22 AM, Jacob Glickman <jhg023 at bucknell.edu> wrote:
> 
> Seeing as `Predicate.not` was just proposed, I think it would be a good
> idea to also introduce `Stream.reject`, which would be logically equivalent
> to calling `Stream.filter` with a negated `Predicate`, but with fewer
> method calls.
> 
> Instead of:
> 
>    Stream.of("", "A", "B", "C")
>         .filter(s -> !s.isEmpty())
>         .count();
> 
> You could call:
> 
>    Stream.of("", "A", "B", "C")
>         .reject(String::isEmpty)
>         .count();
> 
> I welcome any suggestions for better names other than `reject`.  If this
> suggestion is supported, then I'll happily submit an RFE and the code,
> tests, etc.
> 
> - Jacob