add two digits in java code example

Example: sum of digits in java

import java.io.*;
public class sd
{
  public static void main(String [] args)throws IOException
  {
     InputStreamReader hi = new InputStreamReader(System.in);
        BufferedReader in = new BufferedReader(hi);
        System.out.println("Enter the number");
        int num=Integer.parseInt(in.readLine());
    int sum=0;
    while(num>=0)
    {
      int rem=n;
      sum+=rem;
      int quo=n/10;
      n=quo;
    }
    System.out.println(sum);
  }
}