public static void Test2()
        {
            Console.WriteLine("Test2 Start");
            var b = new Ball();
            b.Disp();
            Console.WriteLine("Test2 End");

            bb.Disp();
        }
        public static void Test()
        {
            Console.WriteLine("Test Start");
            for (int i = 0; i < 10; i++)
            {
                var b = new Ball();
                b.Disp();
            }
            Console.WriteLine("Test End");

            bb = new Ball();
            bb = new Ball();
        }