类上的线程“主”中的异常java.lang.NullPointerException

Question

我的代码有问题。

线程“ main”中的异常java.lang.NullPointerException

• 在Game.getHiddenMovieTitle（Game.java:23
• 在Game.gameEnd（Game.java:39）
• 在Main.main（Main.java:14）

我已附加了游戏Java代码。 我知道我需要在Game.getHiddenMovieTitle下进行更改 我试图更改Game.getHiddenMovieTitle的一些代码。

import javax.swing.*;
import java.util.Scanner;

public class Main {
    public static void main(String [] args){
        Game game = new Game("file.txt");

        System.out.println("Let play a mind guess game.");
        System.out.println("Welcome to Guess the Movie!");
        System.out.println("The rules are simple, the computer randomly picks a movie title, and shows you how many letters it's made up of.");
        System.out.println("If you lose 10 points, game over!");
        System.out.println("Let's start!");

        while (!game.gameEnd()){
            System.out.println("You are guessing:" + game.getHiddenMovieTitle());
            System.out.println("You have guessed (" + game.getWrongletter().length()/2 + ") wrong letters:" + game.getWrongletter());

            game.guessLetter();
        }
        if(game.getWon()){
            System.out.println("You win!");
            System.out.println("You have guessed " + game.getMovieTitle() + " correctly.");
        }

        else{
            System.out.println("You have guessed (" + game.getWrongletter().length()/2 + ") wrong letters:" + game.getWrongletter());
            System.out.println("You lost!");
            System.out.println("The movie title was " + game.getMovieTitle());
            System.out.println("Better luck next time.");
        }
    }
}

import java.util.Scanner;

public class Game {
    private String movieGuess;
    private int points;
    private String wrongl;
    private String rightl;
    private boolean won;

    public Game(String path) {
        MovieList movieList = new MovieList(path);
        movieGuess = movieList.getRandomMovie();
        points = 0;
        wrongl = "";
        rightl = "";
        won = false;
    }
    public String getMovieTitle(){
        return movieGuess;
    }
    public String getHiddenMovieTitle() {
        if(rightl.equals("")){
            return movieGuess.replaceAll("[a-zA-Z]", "_");
        }
        else{
            return movieGuess.replaceAll("[a-zA-Z&&[^" + rightl +"]]", "_");
        }
    }

    public String getWrongletter(){
        return wrongl;
    }
    public boolean getWon(){
        return won;
    }
    public boolean gameEnd(){
        if (points >= 10){
            return true;
        }
        getHiddenMovieTitle();
        return false;
    }
    private String inputLetter(){
        System.out.println("Guess a letter");
        Scanner scanner = new Scanner(System.in);
        String letter = scanner.nextLine().toLowerCase();

        if(!letter.matches("[a-z]")){
            System.out.println("That is not a letter. Please enter a letter not a number.");
        }
        else if(wrongl.contains(letter) || rightl.contains(letter)){
            System.out.println("You have already guess that letter.");
        }
        else{
            return letter;
        }
        return letter;
    }
    void guessLetter(){
        String guessedLetter = inputLetter();

        if(movieGuess.toLowerCase().contains(guessedLetter)){
            rightl += guessedLetter + guessedLetter.toUpperCase();
        }
        else{
            wrongl += "" + guessedLetter;
        }
    }
}