我正在嘗試創建一個管理訂票系統的 Java 程序。我有一個電影課：    public class Film {  private String title;  private Double price;  private String ageRestriction;  private double rating;  private String genre;  private String location;  private String screenDay;基于兩個參數（位置和周）創建電影項的 ArrayList 并排序的 FilmList 類    public class FilmList {    public FilmList(ArrayList<Film> filmArrayList) {    this.filmArrayList = filmArrayList;  }  public FilmList (){    this.filmArrayList = new ArrayList<>();  }  public ArrayList <Film> filmArrayList;  public void addFilm(Film films){    this.filmArrayList.add(films);  }  private String showLocation;  private String screenWeek;  public void setScreenWeek(String screenDay) {    this.screenWeek = screenDay;  }  public String getScreenWeek() {    return screenWeek;  }  public void setShowLocation(String location) {    this.showLocation = showLocation;  }  public String getShowLocation() {    return showLocation;  }  public Optional<Film> searchFilm(){    Optional<Film> movieFounded = filmArrayList.stream().filter(i -> i.getLocation().contains(getShowLocation()) &&            i.getScreenDay().contains(getScreenWeek())).findAny();    return movieFounded;  }setShowLocation 參數是通過單擊按鈕來設置的（每個劇院都有一個，而 setScreenWeek 是由 Combobox 設置的圖形單元與控制臺的接口。請注意，如果我按下按鈕而不選擇組合框上的任何內容，則會出現錯誤。