Hello,
I am writing a program that plays 1000 games of craps then prints out win, loss, the amt of rolls for each game, the odds of winning and losing. I am getting the following error:
Exception in thread "main" java.lang.ArrayIndexOutOfBoundsException: 22
at chapt7.Craps.play(Craps.java:94)
at chapt7.Craps.main(Craps.java:17)
I have been over this numerous times and can't seem to figure out the issue, here is my code.
Code:
package chapt7;
// Craps class simulates the dice game craps.
import java.util.Random;
public class Craps
{
public static void main(String[] args)
{
int whenWin[] = new int[22]; //array to store number of rolls that it takes to win each game
//whenWin[0] not used, more than 20 rolls counts is stored in whenWin[21]
int whenLose[] = new int[22]; //array to store number of rolls that it takes to lose each game
//whenLose[0] not used, more than 20 rolls counts is stored in whenLose[21]
//plays 1000 games of craps
for (int i = 0; i < 1000; i++)
play(whenWin, whenLose);
//1000 games complete
//prints out the amount of times game was won on the 'j'th roll
for (int j = 1; j < 22; j++)
{
if (j == 21)
System.out.printf("The amount of times won after roll %d is %d\n", j, whenWin[j]);
else
System.out.printf("The amount of times won on roll %d is %d\n", j, whenWin[j]);
} //end for loop
//prints out the amount of times game was lost on the 'j'th roll
for (int j = 1; j < 22; j++)
{
if (j == 21)
System.out.printf("The amount of times lost after roll %d is %d\n", j, whenLose[j]);
else
System.out.printf("The amount of times lost on roll %d is %d\n", j, whenLose[j]);
} //end for loop
chances(whenWin, whenLose); //caculates and prints out craps chances
avgLengthGame(whenWin, whenLose); //calculates and prints out avg number of rolls/game
}//end main
// create random number generator for use in method rollDice
private static Random randomNumbers = new Random();
// enumeration with constants that represent the game status
private enum Status { CONTINUE, WON, LOST };
// constants that represent common rolls of the dice
private final static int SNAKE_EYES = 2;
private final static int TREY = 3;
private final static int SEVEN = 7;
private final static int YO_LEVEN = 11;
private final static int BOX_CARS = 12;
// plays one game of craps
public static void play(int[] whenWin, int[] whenLose)
{
int myPoint = 0; // point if no win or loss on first roll
Status gameStatus; // can contain CONTINUE, WON or LOST
int rollCount = 1; //counts # of rolls
int sumOfDice = rollDice(); // first roll of the dice
// determine game status and point based on first roll
switch ( sumOfDice )
{
case SEVEN: // win with 7 on first roll
case YO_LEVEN: // win with 11 on first roll
gameStatus = Status.WON;
whenWin[rollCount]++;
break;
case SNAKE_EYES: // lose with 2 on first roll
case TREY: // lose with 3 on first roll
case BOX_CARS: // lose with 12 on first roll
gameStatus = Status.LOST;
whenLose[rollCount]++;
break;
default: // did not win or lose, so remember point
gameStatus = Status.CONTINUE; // game is not over
myPoint = sumOfDice; // remember the point
break; // optional at end of switch
} // end switch
// while game is not complete
while ( gameStatus == Status.CONTINUE ) // not WON or LOST
{
sumOfDice = rollDice(); // roll dice again
rollCount++;
// determine game status
if ( sumOfDice == myPoint ) // win by making point
{
gameStatus = Status.WON;
whenWin[rollCount]++;
}
else
{
if ( sumOfDice == SEVEN ) // lose by rolling 7 before point
{
gameStatus = Status.LOST;
whenLose[rollCount]++;
}
}
} // end while
} // end method play
// roll dice, calculate sum and display results
public static int rollDice()
{
// pick random die values
int die1 = 1 + randomNumbers.nextInt( 6 ); // first die roll
int die2 = 1 + randomNumbers.nextInt( 6 ); // second die roll
int sum = die1 + die2; // sum of die values
return sum; // return sum of dice
} // end method rollDice
//determines chances of wining craps
public static int chances(int[] win, int[] lose)
{
int w = 0; //counts the number games won
int l = 0; //counts the number games lost
for (int i =1; i < 22; i++)
{
w = w + win[i];
l = l + lose[l];
}
System.out.printf("The Chances of winning craps is %d:%d\n", w/w, l/w);
return 0;
}//end method chances
//calculates the average length of each game, i.e. avg amt of rolls to win or lose
public static int avgLengthGame(int[] win, int[] lose)
{
int numOfRolls = 0;
int avg = 0;
for (int i =1; i < 22; i++)
{
numOfRolls = numOfRolls + (win[i] * i) + (lose[i] * i);
}
avg = numOfRolls/1000;
System.out.printf("The Average number of rolls per game is %d\n", avg);
return 0;
}//end method avgLengthGame
} // end class Craps
This is my first class in Java, as you can tell. I am using eclipse, if that is of any help. Any and all input is greatly appreciated. I thank you in advance.
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