求大神这题该怎么做，谢谢

Question

 

Answer 1

package add;
import java.util.*;
 class Rectangle{             //不需要添加public
	  double length;
	  double width;
	 public Rectangle(){}      //有无不重要
	 public Rectangle(double length,double width){  //构造函数
	       this.length=length;
	       this.width=width;}
	    public double area(double length,double width){   //重写方法
	      double Area=length*width;
	    return Area;
	    }
	    public void showInfo(){
	     System.out.println("底面积Area="+length*width);
	    }
	}
	   class Cuboid extends Rectangle{
	   double height;
	   public Cuboid(){}
	   public Cuboid(double length,double width,double height){
	   super(length,width);
	   this.height=height;
	}
	   public double Volume(){
	   double volume=length*width*height;
	   return volume;
	}
	   public void showInfo(){
	   System.out.println("体积volume="+length*width*height);
	}
	}
	  public class test{
	  public static void main(String[] args){
	  Rectangle c2 = new Rectangle(3.1,4.2);
	  c2.showInfo();
	  Cuboid c1 = new Cuboid(3.1,4.2,5.3);
	  c1.showInfo();
}
}