Simple Permutation

import java.util.Scanner;

public class Permutations {

    public static void main(String []args) {

        Scanner scan = new Scanner(System.in);
        System.out.print("Enter first number: ");
        int inputA = scan.nextInt();
        System.out.print("Enter second number: ");
        int inputB = scan.nextInt();

        System.out.println(permute(inputA, inputB));

    }

    public static int permute(int a, int b) {
        if (a < b) throw new IllegalArgumentException("First number must be >= second number.");
        return getFactorial(a) / getFactorial(a-b);
    }

    public static int getFactorial(int a) {
        if (a < 0) throw new IllegalArgumentException("Number must be >= 0");
        return a == 0 || a == 1 ? 1 : a * getFactorial(a-1);
    }


}