java获取json字符串中json对象

String ruleDetail = paperRule.getRuleDetail();
                    if(ruleDetail != null){
                        JSONObject jsonObject = JSONObject.fromObject(ruleDetail);  //转json对象
                        Object paperRules = jsonObject.get("paperRules");   //获取对象中json数组
                        JSONArray jsonArray = JSONArray.fromObject(paperRules);   //遍历拿数据
                        for (int i = 0; i < jsonArray.size(); i++) {
                            JSONObject ruleDetailObj = jsonArray.getJSONObject(i);
                            count += Integer.parseInt((String) ruleDetailObj.get("EASY"));
                            count += Integer.parseInt((String) ruleDetailObj.get("MEDIUM"));
                            count += Integer.parseInt((String) ruleDetailObj.get("HARDER"));
                        }
                        examPaperModel.setQuestionCount(count);
                    }