//Java集合

        List<String> list = new ArrayList<String>();

        list.add("aa");

        list.add("bb");

        Gson gson = new Gson();

        String reslut = gson.toJson(list);

        System.out.println(reslut);

 Buy类中的属性 : Integer id; String name;

 String buyCodes = [{id : 2,name : "aaa"},{id : 3,name : "bbb"}];

 List<Buy> listBuy = gson.fromJson(buyCodes, new TypeToken<List<Buy>>() {}.getType());