private static void Main(string[] args)
        {
            CheapPCBuilder builder = new CheapPCBuilder(); //创建Expensive PC
            //ExpensivePCBuilder builder = new ExpensivePCBuilder();//创建Cheap PC
            PCDirector director = new PCDirector(builder);

            director.CreatePC();

            Console.ReadLine();
        }
        private static void Main(string[] args)
        {
            CheapPCBuilder builder = new CheapPCBuilder();             //创建Expensive PC
            //ExpensivePCBuilder builder = new ExpensivePCBuilder();//创建Cheap PC
            PCDirector director = new PCDirector(builder);

            director.CreatePC();

            Console.ReadLine();
        }