Java Program to find sum of digits of a given number

//Program to find sum of digits of a given number
import java.util.*;
class sumofd
     {
public static void main(String args[])
      {

    int a,r,num,sum=0;
    System.out.println(" Enter a number:");
    Scanner obj=new Scanner(System.in);
    a=obj.nextInt();
    if(a<0)
         num=-a;
    else
         num=a;
    while(num>0)
             {
        r=num%10;
        sum=sum+r;
        num=num/10;
         }
    if(a<0)   
          System.out.println(" sum of digits = -"+sum);
    else
          System.out.println(" sum of digits = "+sum);
     }
   }