by Dinesh Thakur

In this program, we first input the number (Say num = 12345). Next the control reaches the while loop where it checks the condition (num>0) which is true as (12345>0) so the body of the loop is executed.

On First pass,       x=5       Sum=0+5=5           num = 1234

On Second pass,  x=4        Sum=5+4= 9          num = 123

On Third pass,     x=3       Sum=9+3=12         num = 12

On Fourth pass,   x=2       Sum=12+2=14       num = 1

On Fifth pass,      x=1        Sum=14+1=15       num = 0

Finally, when the condition becomes false, the control reaches out of the loop and finally displays the sum of digits of a number. In this program, the number of times the loop will be executed is unknown in advance.

//program to Find Sum of Digits of a Number

import java.util.Scanner; //program uses Scanner class
public class SumDigits
    public static void main(String[] args)
       long num,x,sum=0;
       Scanner input=new Scanner(;
       System.out.println("Enter Number :");
                 x = num%10;
                 sum += x;
                 num /=10;
                 System.out.println("Sum of Digits of Number is :" +sum);

Sum of Digits of a Number in Java Example