code: @Nonnull
    public static EValidity validateMessage (@Nullable final String sMsg)
    {
      final int nLen = StringHelper.getLength (sMsg);
      if (nLen >= 7 && nLen <= 8)
      {
        final byte nNumberSystem = _extractNumberSystem (sMsg);
        if (nNumberSystem >= 0 && nNumberSystem <= 1)
          return EValidity.VALID;
      }
      return EValidity.INVALID;
    }
docs: Validates an UPC-E message. The message can also be UPC-A in which case the
  message is compacted to a UPC-E message if possible. If it's not possible
  an IllegalArgumentException is thrown
  
  @param sMsg
  the message to validate
  @return {@link EValidity}