Menu driven recursive program to perform.(1)Calculate Factorial.(2)sum of digits of a multidigit number.(3)value of x^n.(4)multiplication of 2 numbers.

Menu driven recursive program to perform.
        (1)Calculate Factorial.
        (2)sum of digits of a multidigit number.
         (3)value of x^n.
         (4)multiplication of 2 numbers.

import java.util.*;
class Menudriven{
    public static void main(){
        Scanner sc=new Scanner(System.in);
        System.out.println("Enter 1 for factorial");
        System.out.println("Enter 2 for sum of digits of a multididgit number");
        System.out.println("Enter 3 for value of x^n");
        System.out.println("Enter 4 for multiplication of 2 numbers");
        int a,b,c;
        System.out.println("Enter your choice");
        c=sc.nextInt();
        switch(c){
            case 1:
            System.out.println("Enter a number for factorial");
            System.out.println("Result  =  "+fact(sc.nextInt()));
            break;
            case 2:
            System.out.println("Enter a number for sum of digits of a multididgit number");
            a=sc.nextInt();
            System.out.println("Result  =  "+sum(a));
            break;
            case 3:
            System.out.println("Enter 2 numbers for exponential function");
            a=sc.nextInt();
            b=sc.nextInt();
            System.out.println("Result  =  "+pow(a,b));
            break;
            case 4:
            System.out.println("Enter 2 numbers for multiplication");
            a=sc.nextInt();
            b=sc.nextInt();
            System.out.println("Result  =  "+(a*b));
            break;
            default:System.out.println("Invalid choice");
            break;
        }
    }
        public static int fact(int n){
            if(n==0)
            return 1;
            else
            return n*fact(n-1);
        }//fact
        public static int sum(int n){
            if(n<=9)
            return n;
            else
            return n%10+sum(n/10);
        }//sum
        public static int pow(int a,int b){
            if(b==0)
            return 1;
            else
            return a*pow(a,b-1);
        }//pow
    }//End of class
OUTPUT---
Enter 1 for factorial
Enter 2 for sum of digits of a multididgit number
Enter 3 for value of x^n
Enter 4 for multiplication of 2 numbers
Enter your choice
1
Enter a number for factorial
6
Result  =  720Enter your choice
2
Enter a number for sum of digits of a multididgit number
123456789
Result  =  45Enter your choice
3
Enter 2 numbers for exponential function
2
3
Result  =  8
Enter your choice
4
Enter 2 numbers for multiplication
2
4
Result  =  8