json字符串(注：添加.jar文件或依赖包)：
Sring userOrder＝{"Data":"{\"Data\":[],\"page\":{\"PageIndex\":\"1\",\"PageSize\":\"100\",\"TotalCount\":\"0\"}}","Msg":"获取成功","Code":"10000"}
如想获取PageIndex与PageSize数据，java代码：
JSONObject jsonObject = new JSONObject(userOrder);
JSONObject dataObject = new JSONObject(jsonObject.getString("Data"));
JSONArray jsonarray = dataObject.getJSONArray("Data");
//UserOrderInfo为存储PageIndex,PageSize成员类，构造方法传入数据
List<UserOrderInfo> orderInfo=new ArrayList<>();
String pageIndex="";
String pageSize="";
for(int i=0;i<jsonarray.length();i++) {
JSONObject jsonItem = jsonarray.getJSONObject(i);
pageIndex=jsonItem.getString("PageIndex");
pageSize=jsonItem.getString("PageSize");
orderInfo.add(new UserOrderInfo(pageIndex,pageSize));
}