docs: public static String creditCardNumber(JDefaultCreditCardType type) {
          String ccNumber = null;
          switch (type) {
              case VISA: {
                  StringBuffer tempCC = new StringBuffer("4");
                  tempCC.append(JDefaultNumber.randomNumberString(14));
                  ccNumber = tempCC.append(+generateCheckDigit(tempCC.toString())).toString();
                  break;
              }
              case MASTERCARD: {
                  StringBuffer tempCC = new StringBuffer("5");
                  tempCC.append(JDefaultNumber.randomIntBetweenTwoNumbers(1, 5));
                  tempCC.append(JDefaultNumber.randomNumberString(13));
                  ccNumber = tempCC.append(+generateCheckDigit(tempCC.toString())).toString();
                  break;
              }
              case AMEX: {
                  StringBuffer tempCC = new StringBuffer("3");
                  tempCC.append(JDefaultNumber.randomIntBetweenTwoNumbers(4, 7));
                  tempCC.append(JDefaultNumber.randomNumberString(12));
                  ccNumber = tempCC.append(+generateCheckDigit(tempCC.toString())).toString();
                  break;
              }
              case DISCOVER: {
                  StringBuffer tempCC = new StringBuffer("6011");
                  tempCC.append(JDefaultNumber.randomNumberString(11));
                  ccNumber = tempCC.append(+generateCheckDigit(tempCC.toString())).toString();
                  break;
              }
          }
          return ccNumber;
      }