docs: public static String isbn() {
          StringBuffer stringBuffer = new StringBuffer("09");
          stringBuffer.append(String.format("%06d", JDefaultNumber.randomIntBetweenTwoNumbers(0, 49999)));
          stringBuffer.append(String.format("%02d", JDefaultNumber.randomIntBetweenTwoNumbers(0, 99)));
          String numberString = stringBuffer.toString();
  
  
          int number = Integer.parseInt(numberString);
          int sum = 0;
          for (int i = 2; i <= 10; i++) {
              int digit = number % 10;                // rightmost digit
              sum = sum + i * digit;
              number = number / 10;
          }
  
          // Determine check digit, use X for 10
          String checkDigit = null;
          if (sum % 11 == 1) {
              checkDigit = "X";
          } else if (sum % 11 == 0) {
              checkDigit = "0";
          } else {
              checkDigit = (11 - (sum % 11)) + "";
          }
  
          //  System.out.println("The full ISBN number is " + numberString+checkDigit);
          String returnString = stringBuffer.toString();
          returnString = returnString.substring(0, 1) + "-" + returnString.substring(1, 7) + "-" + returnString.substring(7, 9) + "-" + checkDigit;
  
          return returnString;
      }