code: static boolean isValidCardLength(@Nullable String cardNumber) {
          return cardNumber != null && isValidCardLength(cardNumber,
                  getPossibleCardType(cardNumber, false));
      }
docs: Checks to see whether the input number is of the correct length, after determining its brand.
  This function does not perform a Luhn check.
  
  @param cardNumber the card number with no spaces or dashes
  @return {@code true} if the card number is of known type and the correct length