java-将列表格式化成json字符串

　　　　　　　List<String> list = new ArrayList<>();
            list.add("{'county':'china','age':18}");
            list.add("{'county':'japan','age':28}");
            String data = JSON.toJSONString(list,SerializerFeature.WriteNullListAsEmpty);
            System.out.println(data);