UPCGenerator.java

import java.util.*;
public class UPCGenerator
{
    public UPCGenerator(){
        Scanner scan = new Scanner(System.in);
        String hold = scan.next();
        if(hold.length() == 11){
            System.out.println(UPC(hold) + "");
        }
    }

    public int UPC(String n){
        int oddsSum = 0;
        int evensSum = 0;
        String hold = "";
        for(int i = 0; i < 11; i+=2){
            hold = n.substring(i, i+1);
            oddsSum += Integer.parseInt(hold);
        }
        oddsSum *= 3;
        for(int i = 1; i < 11; i+=2){
            hold = n.substring(i, i+1);
            evensSum += Integer.parseInt(hold);
        }
        int totalSum = oddsSum + evensSum;
        if((totalSum%10) == 0){
            return 0;
        }
        return 10-(totalSum%10);
    }
}