Chapter 2 Question 2.6, Introduction to Java Programming, Tenth Edition Y. Daniel LiangY.

(Sum the digits in an integer) Write a program that reads an integer between 0 and 1000 and adds all the digits in the integer. For example, if an integer is 932, the sum of all its digits is 14. 

Hint: Use the % operator to extract digits, and use the / operator to remove the extracted digit. For instance, 932 % 10 = 2 and 932 / 10 = 93. 

Solution

import java.util.Scanner;

public class Exercise_02_06

{

    public static void main(String[] args)

    {

        Scanner input = new Scanner(System.in);     // Create new Scanner object

        // Prompt the user to enter a number between 0 and 1000.

        System.out.print("Enter a number between 0 and 1000: ");

        int number = input.nextInt();

        // Compute the sum of the digits in the integer.

        int lessThan10 = number % 10;       // Extract the digit less than 10

        number /= 10;                           // Remove the extracted digit

        int tens = number % 10;             // Extract the digit between 10 to 99

        number /= 10;                           // Remove the extracted digit

        int hundreds = number % 10;     // Extract the digit between 100 to 999

        number /= 10;                           // Remove the extracted digit

        int sum = hundreds + tens + lessThan10;

        // Display results

        System.out.println("The sum of the digits is " + sum);

    }

}