[类的定义和调用](%E7%B1%BB%E7%9A%84%E5%AE%9A%E4%B9%89%E5%92%8C%E8%B0%83%E7%94%A8.md) [类的继承](%E7%B1%BB%E7%9A%84%E7%BB%A7%E6%89%BF.md)