Chapter 6 Exercise 2, Introduction to Java Programming, Tenth Edition Y. Daniel LiangY.

*6.2 (Sum the digits in an integer) Write a method that computes the sum of the digits in an integer. Use the following method header: public static int sumDigits(long n) For example, sumDigits(234) returns 9 (2 + 3 + 4). (Hint: Use the % opera- tor to extract digits, and the / operator to remove the extracted digit. For instance, to extract 4 from 234, use 234 % 10 (= 4). To remove 4 from 234, use 234 / 10 (= 23). Use a loop to repeatedly extract and remove the digit until all the digits are extracted. Write a test program that prompts the user to enter an integer and displays the sum of all its digits.

import java.util.Scanner;
 
public class ProgrammingExercise6_2 {
 
 public static void main(String[] args) {
  Scanner input = new Scanner(System.in);
  System.out.print("Enter an integer:");
  long n = input.nextLong();
 
  System.out.println("The sum is " + sumDigits(n));
 }
 
 public static int sumDigits(long n) {
 
  int sum = 0;
  do {
   sum += n % 10;
 
  } while ((n = n / 10) != 0);
 
  return sum;
 
 }
}