class FilenameParser {

	 public long extractIdFromFilename(String filename) throws UnrecognisedFilenameException {
		Matcher matches = pattern.matcher(filename);
		if (!matches.matches() || matches.groupCount() != 1)
			throw new UnrecognisedFilenameException("Could not extract a change script number from filename: " + filename);
		
		return Long.parseLong(matches.group(1));
	 }

	 public  FilenameParser();

}