How can I calculate 0 factorial in a basic factorial code in Java

Here is a basic Java Code which I wrote. I want to know how I can calculate 0! as it can calculate every other number.

import java.util.*;
public class main {

  public static int calcFactorial(int n) {
     int fact = 1;
     for (int i = 1; i <= n; i++) {
     fact = fact * i;
     }

     return fact;
  }

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

      if(n > 0) {
        int factorial = calcFactorial(n);
        System.out.println("Factorial = "+ factorial);
      }

      else {
      System.out.println("Factorial for negative numbers do not exists!");
      }
  }
}

In Java, the factorial of a number n is the product of all positive integers less than or equal to n. By definition, 0! is equal to 1, even though it may seem like an exception.

In the original Java code, factorials were calculated only for n > 0, so 0! was skipped. However, the calcFactorial() method already correctly handles 0! because when n = 0, the for loop doesn't run, and the initial value fact = 1 remains unchanged.

To fix this, we just need to change the condition in the main() method from if(n > 0) to if(n >= 0) so that 0 is included.

Here's the code:

import java.util.*;
public class main {

  public static int calcFactorial(int n) {
     int fact = 1;
     for (int i = 1; i <= n; i++) {
         fact = fact * i;
     }
     return fact;
  }

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

      if(n >= 0) {
        int factorial = calcFactorial(n);
        System.out.println("Factorial = " + factorial);
      }
      else {
        System.out.println("Factorial for negative numbers do not exist!");
      }
  }
}

Now, this code correctly calculates 0! = 1 and handles all non-negative integers properly.