Question

In Java

In mathematics, factorial of a non-negative integer n, denoted by n! , is the product of all positive integers less than or equal to n. For example,

5! = 5 * 4 * 3 * 2* 1 = 120

3! = 3 * 2 * 1 = 6

2! = 2 * 1 = 2

The value of 0! is 1.

Write a program that asks user to enter an integer > 0; if a valid value is entered, it should calculate and display factorial of the number entered. If the user enters an integer <=0, display a message "Invalid entry - valid entry is an integer > 0" and have them re-enter the information.

Answer 1

please check screenshots for better understanding. Any doubts comment below.Thank you.

JAVA CODE:

import java.util.*;
public class Factorial {
   public static void main(String args[])
   {
       System.out.print("Enter an integer >0:"); //Display user to enter an integer >0
       Factorial.fact(); // calling method fact
   }
   public static void fact() // creating method fact
   {
       Scanner sc = new Scanner(System.in);
       int n=sc.nextInt(); // Taking input from user
       if(n<=0)
       {
           System.out.println("Invalid entry - valid entry is an integer > 0");
           System.out.print("re-enter valid value:"); //if the input value is asking user to re-enter value
           Factorial.fact();
       }
       else
       {
           int f = 1;
           for(int i=1;i<=n;i++) //loop for calculating factorial of an integer
           {
               f = f*i;
           }
           System.out.println("The value of "+n+"! is "+f); // printing factorial of an integer
       }      
   }
}