private static Movie buildMovieInfo(
      String category, String title, String description, String studio) {
    Movie movie = new Movie();
    movie.setId(Movie.getCount());
    Movie.incrementCount();
    movie.setTitle(title);
    movie.setDescription(description);
    movie.setStudio(studio);
    movie.setCategory(category);

    return movie;
  }
  public static HashMap<String, List<Movie>> buildMedia(int nCategories) {
    if (null != sMovieList) {
      return sMovieList;
    }
    sMovieList = new HashMap<>();
    sMovieListById = new HashMap<>();

    String title = new String();
    String studio = new String();
    for (int i = 0; i < nCategories; i++) {
      String category_name = String.format("Category %d", i);
      List<Movie> categoryList = new ArrayList<Movie>();
      for (int j = 0; j < 20; j++) {
        String description = "This is description of a movie.";
        title = String.format("Video %d-%d", i, j);
        studio = String.format("Studio %d", (i + j) % 7);
        Movie movie = buildMovieInfo(category_name, title, description, studio);
        sMovieListById.put(movie.getId(), movie);
        categoryList.add(movie);
      }
      sMovieList.put(category_name, categoryList);
    }
    return sMovieList;
  }