//方法三:以父類別為類別,以子類別為其值的型別
        public static void ThreeDispaly()
        {
            Staff Peter       = new FullWork();
            Staff fullWorkder = new Provisional();

            Peter.CalcMoney();       //呼叫父類別的方法
            fullWorkder.CalcMoney(); //呼叫子類別的方法
        }
        /* 方法二:輸出正式員工月薪、兼職員工時薪
         * 實體化子類別物件並直接存取本身所定義的方法
         * 修飾詞用了new和override)calcMoney,
         * 分別算出正式員工的月薪和兼職員工的時薪
         */
        public static void SecDisplay()
        {
            FullWork fullWorker = new FullWork();

            fullWorker.CalcMoney();
            Provisional partWork = new Provisional();

            partWork.CalcMoney();
        }
        //方法一:實作各物件並呼叫showMessage(),只有兼職員工算出時薪
        public static void NonDisplay()
        {
            Staff Peter = new Staff();

            Peter.ShowMessage();
            FullWork fullWorker = new FullWork();

            fullWorker.ShowMessage();
            Provisional partWork = new Provisional();

            partWork.ShowMessage(); //使用覆寫,算出時薪
        }