实现Volume接口

public class Circle  {
protected double radius;

public Circle(double radius)
{
    this.radius=radius;
}
public double perimeter()
{
    return this.radius*2*3.14;
}
public double area()
{
    return this.radius*this.radius*3.14;
    }
public String toString()
{
    return "一个圆，半径"+radius+"周长为"+perimeter()+"面积为"+area();
}
public static void main(String args[])
{
    System.out.println(new Circle(12).toString());
}
}







public class Cylinder extends Circle implements Volume
{
protected double height;
public Cylinder(double radius,double height)
{
    super(radius);
    this.height=height;
   
}
public Cylinder()
{
    this(0,0);
}
public double volume()
{
    return super.area()*this.height;
}
public String toString()
{
    return"体积为"+this.volume();
}
public static void main(String args[])
{
    System.out.println(new Cylinder(12,12).toString());
}
}