12.1面向对象语言的概念 12.1.2继承 图形对象的继承层次结构 GraphicalObj translate scale PolyLine translate scale ClosedGraphics length area Ellipse PolyGon translate area scale area Rectangle Triangle area12.1 面向对象语言的概念 12.1.2 继承 图形对象的继承层次结构 GraphicalObj translate scale PolyLine translate scale length ClosedGraphics area Ellipse translate scale area PolyGon area Rectangle area Triangle … … … … … … B