code: private static String readIO(HttpURLConnection httpUrlConn) throws IOException {
          BufferedReader bufferedReader
                  = new BufferedReader(new InputStreamReader(httpUrlConn.getInputStream(),
                                                             Constant.DEFAULT_CHARSET));
          String line;
          StringBuilder stringBuilder = new StringBuilder();
          while ((line = bufferedReader.readLine()) != null) {
              stringBuilder.append(line);
          }
          // 关闭
          bufferedReader.close();
          httpUrlConn.disconnect();
  
          return stringBuilder.toString();
      }
docs: 读取代码段