Rolling-dice class and driver

alright so i have to write a class and driver that has the user input the number of dice and the number of rolls. and then i have to make an array based off the number of dice * 6. but i get errors. like arrayindexoutofboundsexception.

after i make the array i have to fill it with random numbers and use a histogram to display the program. so the program should look like this Please give any positive help here, im new to this programing this and i would love to learn more. also i cant seem to figure out if statements for the Y/N area to start the program

Welcome to the dice-rolling simulator!

Do you wish to run a simulaton? Y/N: x

that was an invalid option. Please try again.

Do you wish to run a simulation? Y/N: y

How many dise di you wish to roll? 2

How many rolls to you wish to make? 100000

2:@@@@@@

3:@@@@

4:@@@@@@@@@@@

5:@@@@@

6:@@

7:@

8:

9:@@@@@@@@@@

10:@@@

11:@@@@@@@@@@@@@@

12:@@@@@@

//I had to you @ signs because * would not work here

here is my program updated! how do i create the histogram?

package dice;

import java.util.Scanner;
import java.util.Random;

public class Dice 
{
    public static Scanner in = new Scanner (System.in);



    private int dice = 0;
    private int roll = 0;
    private int start;
    private int[] diceAr;
    private int[] rollAr;
    private int simDice;
    private String star = "*";

         //****************************************************************     
    public Dice()
    {
        System.out.println("Welcome to the dice-rolling simulator!\n");
        System.out.println("Do you wish to run a simulation? Y/N; ");
        //start = in.nextInt();


        while (true) {

        System.out.print ("How Many Dice Do You Want To Roll?  ")开发者_开发问答;
            dice = in.nextInt();
            simDice = (dice * 6)-1;
            diceAr = new int[simDice];

                if (dice > 0)
                    break;
          }


        while (true) {

        System.out.print ("How Many Times Do You Want To Roll?  ");
            roll = in.nextInt();
            rollAr = new int[roll];

                if (roll > 0)
                    break;
        }   
    }
    //**********************************************    

      //    public void display()
      //    {
    //
        for ( int i = 0; i < simDice; i++)
      //        {
      //            diceAr[i] = (int)(Math.random()* simDice);
      //            
      //        }
      //        for(int i = 0; i<simDice; i++)
       //       {
       //           System.out.println((i + dice) + ". " + diceAr[i]);
       //       }
       //       
      //    }
     //*********************************************************

    public void display(int diceAr[], int simDice, int roll)
    {
        for(int i=0; i < simDice; i++)
        {
            diceAr[i]  = (int) (Math.random()* simDice);

        }

        for(int i=0; i < roll; i++)
        {

        }

    }

}

Judging from the wording of the questions the program asks and the sample histogram you give, it appears the assignment is to write a program to simulate rolling N dice M times and then make a histogram of the results (i.e. the sum of the numbers on the dice on each roll) of the rolls. So if you enter 3 dice and 100 rolls, it should be as if you rolled 3 dice by hand 100 times.

Even aside from the ArrayIndexOutOfBoundsException issue, that is not what your code is doing. Since this is admitted homework I'm not going to give any code, at least not at this point. But I do have some suggestions/questions that might help you think about the problem better and perhaps you can show us how you've changed your code after thinking about it.

First, consider actually doing the task manually. Find two or three dice and roll them, say, 20 times, and make a histogram of the result on paper. You may find just doing that by itself will give you lots of insight into what your program will have to do and keep track of.

Next, here are some questions that might help focus your thinking:

• If you are rolling 2 dice, what's the lowest possible result of a roll? What's the highest?
• If you are rolling 3 dice, what's the highest and lowest possible result of a roll?
• If you are rolling N dice, what's the highest and lowest possible result of a roll?
• When you simulate a roll, how do you determine what the result of the roll is?
• What array should you track those results in and how big should it be?
• How do you track the results in such a way that you can make a histogram later?
• What, if anything, besides the results do you need to store?

Think this all over, do the "experiment" manually, and then get back to us with what changes you've made to your program and what new questions you may have.

You're declaring diceAr to be size 'dice', but then indexing it with a variable which goes up to 'simDice', which = dice * 6.