Java Program for Calculating Sum of the Digits with Two Approach and time complexity

 

import java.util.Scanner;

public class DigSum {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        System.out.print("Enter the digit : ");
        int num = sc.nextInt();

        long start1 = System.nanoTime();
        System.out.println("Sum is "+sumOfDigits(num));
        long end1 = System.nanoTime();

        System.out.println("Elapsed Time in nano seconds: "+ (end1-start1));

        System.out.print("Enter the digit 2: ");
        String num2 = sc.next();
        long start2 = System.nanoTime();
        System.out.println("Sum is "+sumOfDigitsString(num2));
        long end2 = System.nanoTime();

        System.out.println("Elapsed Time in nano seconds: "+ (end2-start2));


    }

    private static int sumOfDigitsString(String num) {
        int sum = 0;
        for (int i = 0; i < num.length(); i++) {
            sum+= Integer.parseInt(String.valueOf(num.charAt(i)));
        }
        return sum;
    }

    public static int sumOfDigits(int digit){
        int sum =0;
        while (digit!=0){
            int temp = digit%10;
            sum+=temp;
            digit = digit/10;
        }
        return sum;
    }
}

Enter the digit : 123

Sum is 6

Elapsed Time in nano seconds: 14124942         // Using Remainder Method

Enter the digit 2: 123

Sum is 6

Elapsed Time in nano seconds: 540630            // Using String Method

Process finished with exit code 0