//以下两种方法是在继承Door的同时 //MyDoor会出现红色底线 //通过Add unimplemented methods //创建的，这也就是体现了抽象类中的抽象方法 //当子类要继承是必须重写-//the following two methods are inherited and feel at the same time The bottom line// MyDoor will appear red //by the Add unimpleme