By the numbers the 235/40-17 measures 24.40" tall, 235/45-17 measures 25.33" tall, both with 9.25" section width
Nearly an inch taller OD. Are you prepared for the effective axle ratio change, and thus, power loss upon acceleration?
The "J" or JJ symbols you see on a given wheel designates the shape of the wheel's tire mounting(seating) surface.
It does not designate tire size, width, tread depth, treadwear rating, traction, temperature rating, or any other facet or attribute of a tire or tire discussion. Please keep this in mind.

I don't want our NICOnauts to be mis-informed about this stuff