private String findYoungestBackup(Pattern fileNamePattern) {
        List<FTPFile> files = ftp.listFilesInDirectory("/");
        FTPFile youngest = null;

        for (FTPFile file : files) {
            if (fileNamePattern.matcher(file.getName()).matches()) {
                if ((youngest == null) || (youngest.getTimestamp().before(file.getTimestamp()))) {
                    youngest = file;
                }
            }
        }
        if (youngest != null) {
            return youngest.getName();
        } else {
            return null;
        }
    }