继承的概念 Bicycle iS-a relationships Mountain Racing Tandem Bikes Bilkes Bilkes 2005-4-27 北京邮电大学电信工程学院计算机技术中心2005-4-27 北京邮电大学电信工程学院计算机技术中心 -9- 继承的概念 Bicycle Mountain Bikes Racing Bikes Tandem Bikes is-a relationships