Subtract the Product and Sum of Digits of an Integer

/*
Given an integer number n, return the difference between the product of its digits and the sum of its digit
Example 1:

Input: n = 234
Output: 15 
Explanation: 
Product of digits = 2 * 3 * 4 = 24 
Sum of digits = 2 + 3 + 4 = 9 
Result = 24 - 9 = 15

*/
public class Solution
{
    public static int subtractProductAndSum(int num) {
        int product = 1;
        int sum = 0;
        int digit;
        if (num <=0 ) return 0;
        while (num > 0) {
            digit = num % 10 ;
            product*= digit;
            sum+= digit;
            num = num / 10;
        }
        return (product - sum);    
    }
    public static void main(String[] args) {
        System.out.println ("Difference between product and difference : " + subtractProductAndSum(234));
    }
}