People worry about the J-12 - "Will it fit?" for almost any camera.
It's a simple rule - if the camera is Leica standard and has no projections into the area in front of the shutter the lens will fit.
If there are projections in front of the shutter (meters, baffles, shelves) then it may, or may not, depending on the particular arrangement of obstructions and the production run of the J-12. Some are slightly shorter than others. Assume the lens will come go close to touching the shutter.
My J-12 fits on my Bessa-R, reportedly an incompatible combination though in reality this depends on the production run of the J-12. Don't bother trying Leica M-5 or CL, all other cameras are worth a (gentle) test IMHO. The Hexar RF will even do TTL metering with a J-12.
This will apply to your digital camera as well - there is no way for the J-12 to hit a digital sensor with an adaptor set to focus a leica-standard lens. It might, potentially, hit an overly thick shutter, though that seems unlikely to me.