父类与子类的基本应用示范。父类是车类，子类是自行车，摩托车，汽车等。元素有重量，速度等等。适合于初学者理解父类与子类的继承问题。-Parent class and subclass of the basic application demonstration. Parent class is the car class, subclass is bicycles, motorcycles, cars and so on. Element has a weight, speed and so on. Suitable for beginners to understand the parent class and subclass inheritance issues.