code: @Nullable
      public static String removeSpacesAndHyphens(@Nullable String cardNumberWithSpaces) {
          if (isBlank(cardNumberWithSpaces)) {
              return null;
          }
          return cardNumberWithSpaces.replaceAll("\\s|-", "");
      }
docs: Converts a card number that may have spaces between the numbers into one without any spaces.
  Note: method does not check that all characters are digits or spaces.
  
  @param cardNumberWithSpaces a card number, for instance "4242 4242 4242 4242"
  @return the input number minus any spaces, for instance "4242424242424242".
  Returns {@code null} if the input was {@code null} or all spaces.