code: public static void throwExceptionForInvalidValue(final String cssValue)
              throws NullValueException, InvalidValueException {
          if (cssValue == null) {
              throw new NullValueException("the cssValue should not be null.");
          } else if (StringUtil.isBlank(cssValue)) {
              throw new InvalidValueException(
                      "the cssValue should not be blank.");
          }
      }
docs: This method throws {@code NullValueException} if the given
  {@code cssValue} is null or {@code InvalidValueException} if the given
  {@code cssValue} is blank.
  
  @param cssValue
  @throws NullValueException
  @throws InvalidValueException
  @author WFF
  @since 1.0.0