Java覆盖问题

Question

我有类 Rectangle 继承的类 Shape，如下所示:

//Class Shape
public class Shape {
    public double area(){
        return 0.0;
    }
}

//Class  Rectangle 
public class Rectangle extends Shape{

    private int width;
    private int height;
    public Rectangle(int width,int height){
        this.width=width;
        this.height=height;
    }

    public void helloRectange(){
        System.out.println("Hello Rectangle");
    }


    public double area(){
        return this.height*this.width;
    }

}

//And Test Class


public class TestShape {

    public static void main(String []arge){

        Shape shape2=new Rectangle(10,20);

        shape2.helloRectange();


        System.out.println("Rectange is"+shape2.area());
    }

}

我无法使用 shape2 对象调用 shape2.helloRectange(); 方法？谁能详细解释一下。

错误是:

Exception in thread "main" java.lang.Error: Unresolved compilation problem: The method helloRectange() is undefined for the type Shape at com.test.overriding.concept.TestShape.main(TestShape.java:9)

Answer 1

因为 Shape 类没有方法 helloRectange ，更改:

形状 shape2=new Rectangle(10,20);

到:

矩形 shape2=new Rectangle(10,20);

或像这样转换对象:

((Rectangle)shape2).helloRectange();