i dont c any profit for either japan or china to start hostility.
japan military is highly advanced but china is no slouch either,they may loss a battle but u can be assured they are quick learner n may turn the tide with their resolve.
hence it is not japan interests to engage in a prolong conflict with their big neighbour who has grow stronger n perhaps more assertive n ambituous military n economically.
It does not help a peace loving japan is unable to reconcile their past imperial ambition n give the wrong impression that it relish the good old days with their axis partners.
Nazi Germany slaughtered million in their Russian campaign n Stalin led Red Russia fought back inch inch all the way to Berlin,
China did not,the American did that for them n in their civil war resulted in a Mao led communist china to the present day modern china.