public String userPlaylist(String name, GregorianCalendar date) {
        String emailUserPlaylist="";

        for (int i = 0; i < usersList.size(); i++) {
            for (int j = 0; j < usersList.get(i).getPlaylists().size(); j++) {
                if (usersList.get(i).getPlaylists().get(j).getName().equals(name)
                        && usersList.get(i).getPlaylists().get(j).getDateCreation().equals(date)) {
                    emailUserPlaylist = usersList.get(i).getEmail();
                }
            }
        }
        return emailUserPlaylist;
    }