Java Subfactorial !n

Simple Java program to calculate subfactorial of given non-negative integer.

import java.util.Scanner;

// 2018 TheFlyingKeyboard and released under MIT License
// theflyingkeyboard.net
public class Main {

    public static void main(String[] args) {
        Scanner reader = new Scanner(System.in);
        int n;

        System.out.println("Enter a number: ");
        n = reader.nextInt(); //Reads integer from keyboard

        System.out.println("Subfactorial of: " + n + " is equal to: " + subfactorial(n));
    }

    private static double subfactorial(int n){
        double subFact = 0;

        for(int i = 2; i <= n; ++i){
            subFact += Math.pow(-1, i) / factorial(i);
        }

        return subFact * factorial(n);
    }

    private static double factorial(int n){
        int fact = 1;

        for(int i = 2; i <= n; ++i){
            fact *= i;
        }

        return fact;
    }
}