The change JDK-8067969 allowed Stream.count() to short-circuit if the size of the stream is known.

The specification for Stream.count() says:

     * Returns the count of elements in this stream. This is a special case of
     * a reduction and is equivalent to:
     *
     * return mapToLong(e -> 1L).sum();

[markup elided for clarity]

This makes it sound as if count() is defined in terms of mapToLong(e -> 1L).sum(). However, the @apiNote below describes the possibility of short-circuiting which seems to contradict the above.

It would probably be best if mapToLong(e -> 1L).sum() were removed from the specification portion of this method.

This would be a useful example to show in the case where the programmer explicitly wants to avoid the short-circuiting behavior, for example, if there is a peek() with side effects upstream in the pipeline.