Lucky Sevens [Net Change Calculation]

Question

Whenever I execute the program the average change always is 0 and I do not understand why.

/*LuckySevens.java

Simulate the game of lucky sevens until all funds are depleted.
1) Rules:
        roll two dice
        if the sum equals 7, win $4, else lose $1
2) The inputs are:
        the amount of money the user is prepared to lose
3) Computations:
        use the random number generator to simulate rolling the dice
        loop until the funds are depleted
        count the number of rolls
        keep track of the maximum amount
4) The outputs are:
        the number of rolls it takes to deplete the funds
        the maximum amount
        the average net change after 100 rolls
*/

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

public class LuckySevens {
   public static void main (String [] args) {

      Scanner reader = new Scanner(System.in);
      Random generator = new Random();

      int die1, die2,       // two dice
          dollars,          // initial number of dollars (input)
          countAtMax,       // count when the maximum is achieved
          count,            // number of rolls to reach depletion
          maxDollars,       // maximum amount held by the gambler
          averageWin,       // the average net change after 100 rolls
          initialDollars;   // initial amount of money user has 




      // Request the input
      System.out.print("How many dollars do you have? ");
      dollars = reader.nextInt();

      // Initialize variables
      maxDollars = dollars;
      initialDollars = dollars;
      countAtMax = 0;
      count = 0;

      // Loop until the money is gone
      while (dollars > 0){
         count++;

         // Roll the dice.
         die1 = generator.nextInt (6) + 1; // 1-6
         die2 = generator.nextInt (6) + 1; // 1-6

         // Calculate the winnings or losses
         if (die1 + die2 == 7)
            dollars += 4;
         else
            dollars -= 1;


         // If this is a new maximum, remember it
         if (dollars > maxDollars){
            maxDollars = dollars;
            countAtMax = count;
         }

         /* TODO:FIX BELOW STATEMENT
                 it always returns influx as 0 */

         if (count == 100) {
           averageWin = ((maxDollars - initialDollars) / 100);
            System.out.println ("In the first 100 rolls there an average money influx of " + averageWin + " per roll.") ;

         }
      }

      // Display the results
      System.out.println
         ("You went broke after " + count + " rolls.\n" +
          "You should have quit after " + countAtMax +
          " rolls when you had $" + maxDollars + ".");
   }
}

How often have you tested this programm? because its quite possible that you loose some games and then never get back over the maxDollars. Therefore you never change maxDollars aswells as initialDollars. This gives you 0/100 -> 0 — ceekay, Apr 29 '15 at 08:52
possible duplicate of [Division in Java always results in zero (0)?](http://stackoverflow.com/questions/10455677/division-in-java-always-results-in-zero-0) — timrau, Apr 29 '15 at 08:52
There's a good chance the problem is being caused by averageWin being an integer. Try changing it to a float/double instead to prevent it to being cut down the the next lower full number (which might be 0 in your case) and see if that changes the outcome. Might not be the problem but integer division was the first thing to catch my eye — Sossenbinder, Apr 29 '15 at 08:54

score 3 · Accepted Answer · answered Apr 29 '15 at 09:05

3

Make averageWin as double variable.

Change calculation of average win as below

averageWin = ((double)maxDollars - (double)initialDollars) / 100;

answered Apr 29 '15 at 09:05

Yantraguru · Answer 2 · 2015-04-29T09:06:00.503

0

I tried the following to get the correct answer.

Changed type of averageWin

 double averageWin;

And then calculation formula to

 averageWin = (maxDollars - dollars) / 100.0;

This will preserve the precision and give you the correct answer.

edited Apr 29 '15 at 09:06

answered Apr 29 '15 at 08:54

Yantraguru

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Lucky Sevens [Net Change Calculation]

2 Answers2