Question

How to sum the digit of a factorial of a number in Java

Answer 1

public class Main {
    public static int sumDigits(long num) {
        int sum = 0;
        
        while (num != 0) {
            sum += num % 10;
            num /= 10;
        }
        
        return sum;
    }

    public static long factorial(long n) {
        if (n == 1 || n == 0) {
            return 1;
        }
        return n * factorial(n - 1);
    }

    public static void main(String[] args) {
        long number = 9;
        long result = factorial(number);

        System.out.println("factorial = " + result);
        System.out.println("sum digits = " + sumDigits(result));
    }
}

  
  
/*
run:
  
factorial = 362880
sum digits = 27
  
*/

 

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