我在shape抽象類里定義了兩個方法：

public abstract void girth();

public abstract void area();

之后我用Rectangle類繼承shape抽象類就出現這種錯誤：

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？