The chances of Japan and China going to war over these resource rich islands are pretty slim. However it's not to saw it will never happen as economically tied nations have gone to war against each other before. Also ascending or resurgent nations do tend to get quite assertive (Most well known being Germany & Japan during the 20th century for example, while Russia and China are both being quite assertive now).
One of China's great strengths was it's patience in it's rise to power. I believe in this case China is simply making a lot of noise to prevent Japan from actually doing anything to exploit the resources around the islands in dispute. Also I think China (along with other countries) can sense the US retreating somewhat from being the worlds self appointed policemen and getting her allies to do some of the work instead (but still providing logistical and intelligence support) while it get's back in shape. China still knows that it's military has a lot of catching up to do but if they follow the patient path they have been following then it's not inconcievable to think their military will rival or even displace US naval power from at least the Eastern Pacific region in the coming decades. Right now though the PLAN is just a brown water navy though it does have some pretty powerful ships, land based fighter jets and subs (mostly bought from Russia). The Chinese definately need to improve their submarine acoustic signature. Apparently it's about 2-3 decades behind Western and Russian submarines. http://www.wired.com/dangerroom/2011/12/china-submarines/
