CSC 143 A useful technique for catching typing errors is to

CSC 143

A useful technique for catching typing errors is to use a check digit. For example, International Article Number 13 (EAN 13) uses the last digit (also known as checkdigit) to validate the correctness of the first 12 digits. For more info on EAN 13. see: http://en.wikipedia.org/wikki/International Article Number (EAN If EAN13 is 4006381333931 the check code is computed as follows: The nearest multiple of 10 that is equal or higher than the sum, is 90. Subtract them: 90 - 89 = 1, this is the last digit of the barcode. Write a Java program that asks the user for a EAN13 and validates it as either correct or incorrect (display a message accordingly). Your program should continue to run, to validate multiple EAN 13 numbers, untill the user decides to exit the program, by entering \'Q\' or \'Quit. Your program is allowed to use any of the concepts covered through the first 8 Chapters and topics from the appendices from our class text book.

Solution

import java.util.*;
import java.io.*;
public class HelloWorld{
  
    //fucntion to check for EAN number
    public static boolean isEAN(String number)
    {
        //declare required v ariables
        int sum=0;
        int digit=0;
        int newSum=0;
        //get last digit
        int firstDigit=Character.getNumericValue(number.charAt(12));
      
        //loop through digits and get the sum
        for(int i=0;i<number.length()-1;i++)
        {
            digit=Character.getNumericValue(number.charAt(i));
            if(i%2==0)
            sum+=digit*1;
            else
            sum+=digit*3;
        }
      
        //check if difference is equal to last digit
        newSum=(10 - sum % 10) + sum;
        if(Math.abs(newSum-sum)==firstDigit)
        return true;
        return false;
    }

     public static void main(String []args){
         boolean flag=true;
       
         //loop until until user enters Q
    do{
        //prompt user for input
        System.out.print(\"Enter a EAN number: \");
        String number;
        Scanner input=new Scanner(System.in);
        number=input.next();
      
        //check if user entered Q
        //if yes,exit
        if(number.equals(\"Q\"))
        flag=false;
        //else check if user entered a valid number
        else if(number.length()!=13)
        {
            System.out.println(\"Enter a valid number\");
        }
        //if valid number entered, pcall EAN method
        else
        {
        if(isEAN(number))
        System.out.println(number+\" is EAN \");
        else
        System.out.println(number+\" is not EAN\");
        }
     }while(flag);
}
}

Sample Output:

Enter a EAN number: q213                                                                                                                                                                                                                               

4Enter a valid number                                                                                                                                                                                                                                  

Enter a EAN number: 133456768                                                                                                                                                                                                                          

9Enter a valid number                                                                                                                                                                                                                                  

Enter a EAN number: 4006381333931                                                                                                                                                                                                                      

4006381333931 is EAN                                                                                                                                                                                                                                   

Enter a EAN number: 400638133930                                                                                                                                                                                                                       

12Enter a valid number                                                                                                                                                                                                                                 

Enter a EAN number: 4006381333930                                                                                                                                                                                                                      

4006381333930 is not EAN                                                                                                                                                                                                                               

Enter a EAN number: Q