Question

所以我正在编写一个掷骰子的游戏，这需要我掷两个骰子并返回骰子的总和。滚动7或11赢得游戏，滚动2,3或12然而将失去你的游戏。滚动4,5,6,8,9,10将＆＃34;建立点＆＃34;用户继续滚动，直到他们滚动相同的号码，直到他们滚动7，在这种情况下他们输了。

在我的情况下，我得到一个说

的例外

"Exception in thread "main" java.lang.NullPointerException
at Craps.getSum(Craps.java:24)
at Craps.playRound(Craps.java:29)
at Craps.main(Craps.java:70)
C:\Users\owner\AppData\Local\NetBeans\Cache\8.2\executor-snippets\run.xml:53: Java returned: 1
BUILD FAILED (total time: 2 seconds)"

我的Die课程看起来像这样：

import java.util.Random;
public class Die 
{
    private int number;
    private Random generator;

    public Die()
    {
        generator = new Random();
        roll();
    }

    public int getNumber()
    {
        return number;
    }

    public void roll()
    {
        number = generator.nextInt(6)+1;
    }
}

我的掷骰子游戏看起来像这样：

import java.util.Scanner;

public class Craps 
{
    private Die die1;
    private Die die2;

    private void rollDice()
    {
        die1.roll();
        die2.roll();
    }

    private int getSum()
    {
        return (die1.getNumber() + die2.getNumber());
    }

    public void playRound()
    {
        if (getSum() == 7 || getSum() == 11)
        {
            System.out.println("You rolled a " +getSum()+ "! You win!!!");
        }
        else if(getSum() == 2 || getSum() == 3 || getSum() == 12)
        {
            System.out.println("You rolled a " +getSum()+ " You lose.");
        }
        else if(getSum() == 4 || getSum() == 5 || getSum() == 6 || getSum() == 8 || getSum() == 9 || getSum() == 10)
        {
            int established = getSum();
            System.out.println("Establishing the point... Re-Rolling...");
            rollDice();

            do
            {
                rollDice();
                System.out.println("You rolled a " +getSum());
            }
            while (getSum() != established && getSum() != 7);

            if (getSum() == established)
            {
                System.out.println("You rolled a " +getSum()+ " which is also the established point, You win!");
            }
            else if(getSum() == 7)
            {
                System.out.println("You rolled a 7 after establishing the point, you lose.");
            }

        }       
    }

    public static void main(String[] args)
    {
        Craps game = new Craps();
        Scanner scan = new Scanner(System.in);
        System.out.println("Welcome to the game of Craps!");
        System.out.println("Would you like to play a game? (Y/N");
        String input = scan.nextLine();
        if (input.equalsIgnoreCase("Y"))
        {
            game.playRound();
        }
        else
        {
            System.out.println("Okay see you next time!");
            System.exit(1);
        }
    }
}

Answer 1

private Die die1;
private Die die2;

持有空引用。

我的Rolling Craps代码出了什么问题？

1 个答案: