4-3抽象类课后练习
我在shape抽象类里定义了两个方法：
public abstract void girth();
public abstract void area();
之后我用Rectangle类继承shape抽象类就出现这种错误：
Multiple markers at this line
- implements chouXiangLei4_3.shape.girth
- The method girth() of type Rectangle must override or implement a supertype
method
是怎么一回事呢？
