if that war was to break out. it would be the start of ww3. china is a power house. and if they put the manufacturing plants to warfare production. they could very well wipe japan off the map.

China's defence spending has doubled every year since 1989. If war broke out china would I blieve have plently of anti satellite missiles ready, that would really hurt the US/japan tech based warfare. 

A key element of China's defenses is its growing stockpile of ballistic and cruise missiles that have enough range to blanket much of Asia. its DF-21D "aircraft carrier killer" missile, That has a range of 3000 km and is specially designed to target the U.S. navy.