public static ArrayList<String> readDomains(String filename){
        ArrayList<String> list = new ArrayList<String>();
        try {
            BufferedReader reader = new BufferedReader(new FileReader(new File(filename)));
            while(true){
                String mail = reader.readLine();
                if(mail == null) break;
                list.add(mail.split("@")[1].toLowerCase());
            }
        } catch (FileNotFoundException e) {
        } catch (IOException ex) {
        }
        return list;
    }