我有兩個list分別保存了兩個對象列表provinceList保存了省的信息（id，name），universityList保存了該省下的大學信息（id，name）】想將其轉(zhuǎn)換成如下格式的json字符串，應該如何做？？？？{"provinces":[?? ??? ??????????????? {"id":1,"name":"北京"}，?? ??? ??????????????? {"id":2,"name":"上海"}????????????????????????...........?? ??? ?????????????? ]，?? ??? ??? "universities":[?? ??? ???????????????? {"id":1, "name":北京大學},?? ??? ???????????????? {"id":2, "name":人民大學},?????????????????????????...........?? ??? ?????????????? ]?? ??? ?? }