Japan has since WW2 been a militarily and monetarily a subservient tribute state to the USA. Watch Princes of the Yen

China in contrast firstly had to establish secure and true sovereignty which initially was gained from behind the USSR cold war with the west and acquisition of nukes and seizure of Tibet to prevent the west positioning its nukes there. Only subsequent to the fall of the Berlin wall and death of Mao has China had the national security to develop economically and under Deng they began the process that has since seen the most incredible economic development in modern history. Mainland China had for a long time since 1945 played it carefully because the USA did not even recognise its legitimacy until the 1970s...instead siding with the Nationalists in Taiwan who were much more compliant to and aligned with western imperialist imperatives. Before 1945 they had already endured the 100 years of humiliation that followed the briutality of the Opium Wars and the subjugation of China to western imperialism- - read up on the Opium Wars if you want to understand modern China! Post WW2 the seat on the UN security council was expected by the European imperialists and the USA to be occupied by compliant Chinese Nationalists, not the CCP...but following Hiroshima and the evacuation of Japanese forces who had occupied and enslaved much of China since the early 1930s the Communists under Mao swept the nation and took power with the Nationalists fleeing to Taiwan which the Chinese Treasury gold. Read some history to understand the past, present and the likely future...its a fascinating pursuit!