I do think that Japan and China will have a limited war at some point to resolve the issues of the disputed islands.
I also think that China will overwelm Japan to such an extent that they will just back down and not try to extend the war further. Nuclear weapons still stop any large scale wars from happening, but large skirmishes should be possible.
Numbers don't matter , what it matter it's the technology available.
And the JSDF even as tiny as it is will put China back to it's place.
Also , Japan has allies , China ? Not. Russia won't move a finger in this , but will rather join the opposite side.