private boolean isExistingLogin(String login){
        
        if (this.file.exists()) {
                try {

                    BufferedReader br = new BufferedReader(
                            new InputStreamReader(
                            new FileInputStream(this.file)));
                    String ligne;
                    while ((ligne = br.readLine()) != null) {
                        String[] resultSplit = ligne.split(":");
                        if (login.equals(resultSplit[0])){
                            br.close();
                            return true;
                        }
                    }
                    br.close();
                    return false;
                } catch (Exception e) {
                    System.out.println(e.toString());
                }

            }
        
        return false;
    }