I doubt China has the wish to invade other countries, her priority is raising the standard of living for her rural poor, educating them, providing them a chance to share the country's rising wealth. Her neighbours should not fear China, she has no expansion plans.
Historically, the Han Chinese have never been expansionist, in the sense the word's used with the other big empires like Pax Romana or Pax Britannica. The stronger and wealthier it was, like during Tang or Northern Song, the more pacifist it was, the more it was subjected to opportunist attacks by surrounding tribal nations. Even at its most expansionist, the ruling perpetrators were actually non-Hans, e.g. Mongols and Manchus.
China's 2 overriding priorities today are: 1) raise the standard of living of the poor and ameliorate the wealth gap; 2) guard the territorial integrity of lands she deems to be hers. Both also serve the nationalist agenda of preserving party survival.
It is (2) that's causing their neighbours to be apprehensive, to label it 'expansionist'. But the Chinese have long memories of past humiliations of land grabs by the West and Japan at gunpoint, and from their perspective it's merely reclaiming their rightful territories, not invading other nations' land. Other than righting past wrongs, there's no reason why China needs more land; their leaders already have their hands full dealing with 1.3 bil people and 9.7 million sq km of land that is subject to every known kind of natural disaster.