Stream Method Proposal: long count(Predicate<? super T> predicate)

[Jacob Glickman]

 Hello!

I see myself having to often call count() as a terminal operation on a
Stream immediately after performing a filter operation. How feasible would
it be to add an overloaded count() method that accepts a Predicate, which
it uses as a filter before returning the count of elements in the Stream?
If this is supported, I'd gladly create the webrev & tests for it!

I suppose the method signature can be something along the lines of:

    long count(Predicate<? super T> predicate)

It would also seem reasonable to give this method to IntStream,
DoubleStream, and LongStream, but allowing them to use IntPredicate,
DoublePredicate, and LongPredicate respectively.

Thanks,

Jacob Glickman