public static void UI()
        {
            Console.Clear();
            int number;

            Console.Write("Faktoriyel Hesabı Yapılacak Sayı: ");
            number = int.Parse(Console.ReadLine());
            var factorialCalculator = FactorialCalculator.CreateAsSingleton();

            factorialCalculator.Calculate(number);
        }
 public static FactorialCalculator CreateAsSingleton()
 {
     return(_factorialCalculator ?? (_factorialCalculator = new FactorialCalculator()));
 }