編寫一個圓類Circle，該類擁有： ①一個成員變量 Radius（私有，浮點型）； // 存放圓的半徑； ②兩個構造方法 Circle( ) // 將半徑設為0 Circle(double r ) //創建Circle對象時將半徑初始化為r

//圓
package Test;
import java.util.Scanner;
public class Circle
{
    private double Radius;
    public void setRadius(double r)
    {
        this.Radius=r;
    }
    public Circle()//無參構造方法
    {
        this.Radius=0;//初始化為0
        System.out.println("圓!");
    }
    public Circle(double r)//帶參構造方法
    {
        this.Radius=r;
    }
    public double getRadius()
    {
        return Radius;
    }
    public double getArea()//求圓的面積
    {
        double r=this.Radius;
        return r*r*3.14;
    }
    public double getPerimeter()//求圓的周長
    {
        return this.Radius*3.14*2;
    }
    public void showCircle()
    {
        Scanner cin=new Scanner(System.in);
        System.out.println("請輸入半徑:");
        this.setRadius(cin.nextInt());
        System.out.println("半徑="+this.getRadius());
        System.out.println("周長="+this.getPerimeter());
        System.out.println("面積="+this.getArea());
    }
}
//圓柱

package Test;
import java.util.Scanner;
public class Cylinder extends Circle {
    private double Height;//圓柱高
    public void setHeight(double h) {
        this.Height = h;
    }
    public Cylinder (double r, double  h) //構造方法
    {
        this.Height=h;
        this.setRadius(r);
    }
    public double getHeight() {
        return Height;
    }
    public double getVolume( ) //求體積
    {
        return this.getArea()*this.Height;
    }
    public void showCylinder()
    {
        Scanner cin=new Scanner(System.in);
        System.out.println("請輸入底面圓半徑:");
        this.setRadius(cin.nextInt());
        System.out.println("請輸入高:");
        this.setHeight(cin.nextInt());
        System.out.println("底面半徑="+this.getRadius());//子類可以通過調用父類的公有成員函數間接訪問父類的私有成員變量

        System.out.println("高="+this.getHeight());
        System.out.println("圓柱的體積="+this.getVolume());
    }
}
//主程序

package Test;
public class Test {
    public static void main(String[] args)
    {
        Circle c=new Circle();
        c.showCircle();
        Cylinder cd=new Cylinder(1.0,1.0);//給圓柱的底面圓半徑和高初始化
        cd.showCylinder();
    }
}
//本題中所有的this.都可以刪除