What is wrong with my Rolling Craps code?

Question

So I am coding a game of craps which requires me to roll two dice and return the sum of the dice. Rolling a 7 or 11 wins you the game, rolling a 2, 3, or 12 however will lose you the game. Rolling a 4, 5 ,6, 8, 9, 10 will "Establish the point" where the user continues to roll until they roll the same number that was established or until they roll a 7, in which case they lose.

In my case, I get an exception that says

"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)"

My Die class looks like this:

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;
    }
}

And my game of craps looks like this:

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);
        }
    }
}

You don't get a "null error" - you get an exception that tells you exactly what went wrong and where. You should include that in the question. — John3136, Apr 07 '17 at 05:58
Possible duplicate of [What is a Null Pointer Exception, and how do I fix it?](http://stackoverflow.com/questions/218384/what-is-a-nullpointerexception-and-how-do-i-fix-it)? Hint: Where is a `new Die()`? — IQV, Apr 07 '17 at 06:11
I Don't think it's valid to mark this question as duplicate. — joey rohan, Apr 07 '17 at 06:14

score -4 · Answer 1 · answered Apr 07 '17 at 06:11

-4

private Die die1;
private Die die2;

Holds a null reference.

answered Apr 07 '17 at 06:11

joey rohan

3,505
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May I know the reasons for down vote? – joey rohan Apr 07 '17 at 06:17

What is wrong with my Rolling Craps code?

1 Answers1