java 16进制数求和工具类

 /**
       * 16求和
       * @param hexdata
       * @return
       */
      public static String makeChecksum(String hexdata) {
          if (hexdata == null || hexdata.equals("")) {
              return "00";
          }
          hexdata = hexdata.replaceAll(" ", "");
          int total = 0;
          int len = hexdata.length();
          if (len % 2 != 0) {
              return "00";
          }
          int num = 0;
          while (num < len) {
              String s = hexdata.substring(num, num + 2);
              total += Integer.parseInt(s, 16);
              num = num + 2;
          }
          return hexInt(total);
      }

      private static String hexInt(int total) {
          int a = total / 256;
          int b = total % 256;
          if (a > 255) {
              return hexInt(a) + format(b);
          }
          return format(a) + format(b);
      }

      private static String format(int hex) {
          String hexa = Integer.toHexString(hex);
          int len = hexa.length();
          if (len < 2) {
              hexa = "0" + hexa;
          }
          return hexa;
      }