Fims

Film.java

class Film implements FilmInterface {
  
  public String getTitle() {}
  
  public Float getRating() {}
  
  public int addRating(int rating) {}
  
}

FilmCollection.java

class FilmCollection implements FilmCollectionInterface {
  
  String[] sorts = { "title", "rating", "year", "genre" };
  
  // also you can use a constants:
  // public static final String SORT_TITLE = "title";
  // public static final String SORT_RATING = "rating";
  // public static final String SORT_YEAR = "year";
  
  public void getFilms(String sort)
  {
    // check is the sort argument exist in allowed sorts
    if ( ! ArrayUtils.contains( sorts, sort ) ) {
        // throw an exception
        throw new IllegalArgumentException("invalid sortation argument")
     }
    
    switch (sort) {
      case "year":
        // sort by title
        break;
        
      case "rating":
        // sort by rating
        break;
        
      case "genre":
        // sort by genre
        break;
        
      default:
        // sort by title
        break;
        
      // return sorted films
  }
  
  // examples:
  // https://stackoverflow.com/questions/19471005/sorting-an-arraylist-of-objects-alphabetically
  // https://stackoverflow.com/questions/13380908/sort-arraylist-of-complex-objects-alphabetically   
  private function sortByRating()
  {
      // sort by rating
    Collections.sort(films, new Comparator<Film>() {
        public int compare(Film f1, Film f2) {
            return f1.getRating().compareTo(f2.getRating());
        }
    });
  }
}
  

FilmInterface.java

import java.lang.*;

public interface FilmInterface
{
  public void getTitle();
  public void getYear();
  public void getGenre();
  
  public void addRating(int rating); // add rating to array
  public void getRating(float rating) // return sum of the ratings devided by number of elements
}