private FTPFile getLatestFilename(FTPClient ftpClient) throws Exception {
    ftpClient.changeDirectory(filePath);
    // ftpClient.listNames();
    FTPFile[] files = ftpClient.list("*.zip");
    System.out.println("files.length " + files.length);
    if (files.length == 0) {
        throw new Exception("Unable to locate a single file for mask: [" + fileMask + "] at location: [" + filePath + "].");
    }
    Arrays.sort(files, new FTPFileByDate());
    FTPFile ftpFile = files[files.length - 1];
    return ftpFile;
}

private class FTPFileByDate implements Comparator<FTPFile> {
    @Override
    public int compare(FTPFile f1, FTPFile f2) {
        return f1.getModifiedDate().compareTo(f2.getModifiedDate());
    }
}