Split List on lists by property

splitFilmsByGenres.java

private ArrayList<FilmsByGenre> splitFilmsByGenres(ArrayList<FilmItem> films) {
    Map<String, ArrayList<FilmItem>> filmListMap = new HashMap<>();

    for (FilmItem film : films) {

        ArrayList<FilmItem> temp = filmListMap.get(film.getGenreName());

        if (temp == null) {
            temp = new ArrayList<>();
            filmListMap.put(film.getGenreName(), temp);
        }

        temp.add(film);
    }

    ArrayList<FilmsByGenre> filmsByGenres = new ArrayList<>();

    for (Map.Entry<String, ArrayList<FilmItem>> filmEntry : filmListMap.entrySet()) {
        FilmsByGenre genreFilms = new FilmsByGenre(filmEntry.getKey(), filmEntry.getValue());
        filmsByGenres.add(genreFilms);
    }

    return filmsByGenres;
}