Case Study IV - Solution
COMP 1010 Home > Java Fundamentals
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IntroductionThis page contains a sample solution to Case Study IV along with a detailed description on each step to go from the Case Study IV to the sample solution. All the steps apply knowledge that can be gained from the sources listed in the overview section of this page.
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Sample Solution
This section goes over, in detail, the changes made to the Code to fix.
Declare needed variables
The first thing you will want to do is declare an integer array and an integer. Do this by adding the following code to your variables list in the main method:
String isbnArray[]; //array to hold 9-digit ISBN numbers
int counter; //a counter to keep track of how many times to loop the program
Add Input from the User
You will now need to ask the user how many check digits they would like to enter. I did this with the following code:
temp = JOptionPane.showInputDialog
("How many ISBN check digits would you like to calculate?");
counter = Integer.parseInt(temp);
As you can see, I reused the 'temp' variable since it is not needed for more after the input is saved as an integer.
After the input is taken, I then parse the String into an integer variable called 'counter'.
Create the Array
Now that we know how many numbers to read in, we can create the array with a size of 'counter':
isbnArray = new String[counter];
Input Loop
We can now start taking data from the user
This time, instead of taking the user's input an calculating the check digit right away, we'll store it away for later (in an Array).
//loop 'isbnArray.length' times
for(int i=0; i < isbnArray.length; i++)
{
temp = JOptionPane.showInputDialog
("Enter the first 9 digits of a 10-digit ISBN number.");
//confirm input
System.out.println ("You have entered " + temp + ".");
//store ISBN in an array for later calculation
isbnArray[i] = temp;
}//end for-loop
Calculation Loop
All that is left for the calculation is to take each number out of the array and pass it to the 'calcISBN' method.
//run the calcISBN method on every value in the array
for(int i=0; i < isbnArray.length; i++)
{
//method call to calculate the checkDigit
//send the method the isbn in the array at position i
calcISBN( isbnArray[i] );
//line to separate entries
System.out.println("\n---------------------------");
}//end for-loop
Modify Output
To finish up, we will remove some of the output in the 'calcISBN' method by commenting it out.
I have found it to be a good practice to only comment out your output rather than delete it all together. This way, if you need it back later (say to debug code), you can save yourself a lot of time
//System.out.println (digit + " * " + i + " for a running total of " + total);
System.out.println ("\nFor " + temp +
/*"The weighted total is: " + total +*/
"\n\nThe check digit is : " + checkDigit +
"\n\nThe 10-digit ISBN is: " + temp + checkDigit);
After removing some of the output, I had added some new lines and other formatting to clean up the output.
Sample Solution Code
import javax.swing.*;
import java.util.Date;
/**
* calculate a check digit for ISBNs
*
* @author: 1010 Instructors
* @modified by: Gregor McKenzie
* @version: 2007-December
*/
public class CaseStudy4_ISBN_Solution
{
/**
* PURPOSE: inputs a 9-digit ISBN, calculates the check digit and outputs a 10-digit ISBN
*/
public static void main (String [] args)
{
//variables declared here
String temp = ""; //temporary input string
String isbnArray[]; //array to hold 9-digit ISBN numbers
int counter; //a counter to keep track of how many times to loop the program
//get input
temp = JOptionPane.showInputDialog
("How many ISBN check digits would you like to calculate?");
counter = Integer.parseInt(temp);
isbnArray = new String[counter];
//loop 'counter' times
for(int i=0; i < isbnArray.length; i++)
{
temp = JOptionPane.showInputDialog
("Enter the first 9 digits of a 10-digit ISBN number.");
//confirm input
System.out.println ("You have entered " + temp + ".");
//store ISBN in an array for later calculation
isbnArray[i] = temp;
}//end for-loop
//run the calcISBN method on every value in the array
for(int i=0; i < isbnArray.length; i++)
{
//method call to calculate the checkDigit
//send the method the isbn in the array at position i
calcISBN( isbnArray[i] );
//line to separate entries
System.out.println("\n---------------------------");
}//end for-loop
System.out.println("\nProgrammed by COMP 1010 Instructors");
System.out.println("Date: " + new Date());
System.out.println ("*** End of Processing ***");
}//end main
public static void calcISBN(String temp)
{
//variables declared here
int isbn; //9-digit ISBN
int total = 0; //total of isbn number when each digit is multiplied by check value
int digit; //isolated ISBN digit
int checkDigit; //value of total%11(as per ISBN standard)
isbn = Integer.parseInt(temp);
//System.out.println ("\nFor " + temp + ", the weighted value of the ISBN is:");
//the loop to calculate the sum of the products of numbers
for(int i=9; i >= 1; i--)
{
//isolate next digit and multiply by i
digit = (isbn % 10);
total = total + digit * i;
isbn = isbn / 10;
//System.out.println (digit + " * " + i + " for a running total of " + total);
}// end for-loop
//calculate check digit
checkDigit = total % 11;
//output weighted total and check digit
System.out.println ("\nFor " + temp +
/*"The weighted total is: " + total +*/
"\n\nThe check digit is : " + checkDigit +
"\n\nThe 10-digit ISBN is: " + temp + checkDigit);
}//end calcISBN
}//end class
Links To Case Studies
Case Study I: Day One at Funky Books Inc.
Case Study II: Day Two at Funky Books Inc.
Case Study III: Day Three at Funky Books Inc.
Case Study IV: Day Four at Funky Books Inc.
