Seeking war with Japan is suicidal for China.
China can prevent the US fleet from approaching, but China’s navy falls far short if it needs to secure its lifelines, especially to suppliers of oil. In a protracted war, China would run out of gas rapidly.
China’s economy is so dependent on far away markets that it cannot keep people employed when access to these markets is shut down. It would result in a massive economic followed by a social crisis that would topple the rule of the communists. While for Europe and the US a Chinese shutdown would mean a glut of oil on the markets, a huge opportunity to restart manufacturing, an immediate strengthening of the Atlantic coalition.
China would not be trusted anymore with the crown jewels for decades if it were to attack Japan.
I can also see that many in the Chinese leadership may not see the gravity of their station, but they really have no way to win any such war if it were to involve the US.
It really is just bluster and posturing, dangerous to Japanese economic interests only. China may demand of its trade partners that they start disliking Japan as well, by increasing trade with China at the expense of Japan. That may well be the extent of the game.