Variable won't increment. - Greatest Common Divisor in java

Question

My task is to accept 2 fractions and sum them and then return in the simplest form.

For some reason the line "gcd = i;"does not run while executing and hence my program enters an infinite loop when I run it.

import java.util.*;

class fraction {
    public static void main(String[] args) {
        int num1, den1, num2, den2;
        Scanner sc = new Scanner(System.in);
        /* System.out.print("Enter first numerator:");
        num1 = sc.nextInt();
        System.out.print("Enter first denominator:");
        den1 = sc.nextInt();
        System.out.print("Enter second numerator:");
        num2 = sc.nextInt();
        System.out.print("Enter second denominator:");
        den2 = sc.nextInt(); */

        num1 = 1;
        den1 = 2;
        num2 = 1;
        den2 = 2;
        System.out.print(num1 + "/" + den1 + " + " + num2 + "/" + den2 + " is equal to ");

        int num = num1 * den2 + den1 * num2;
        int dum = den1 + den2;
        System.out.println(num + "/" + dum);
        System.out.println(num % dum);

        int gcd = 2;
        while (num % dum == 0) {
            for (int i = 1; i < num && i < dum; ++i) {
                if (num % i == 0 && dum % i == 0) {
                    gcd = i;//This line.
                    System.out.println(gcd + " " + i);
                }
            }
                
            num = num / gcd;
            dum = dum / gcd;
        }

        System.out.println(num + "/" + dum);
    }
}

Answer 1

You always enter in gcd = i;

the problem is that at the end of the statement you have

num1    1
den1    2
num2    1
den2    2
num     2
dum     2
gcd     1

so num = num/gcd returns 2 and also dum = dum/gcd = 2. So you cannot go out of the while cycle

Maybe you can solve in the for cycle putting for (i =2... )