编写一个Java源程序，该源文件中有3个类：Circle类、Cylinder类和Test2类，分别用来刻画“圆形”、“圆柱体”和测试用类，具体要求如下： a) Circle类具有类型为double的半径（r）属性，具有返回周长(getPerimeter)、面积(getArea)的功能，其中求周长和求面积方法分别使用实例方法和类方法两种方式实现。自行补充类的get/set方法、有参/无参构造方法、toString方法。 b) 以组合方式定义圆柱体Cylinder类，具有高（h）、底面(undersurface)属性，底面是圆类型，具有返回表面积（getSurfaceArea）和体积(getVolumn)方法。自行补充类的get/set方法、有参/无参构造方法、toString方法。 c) 编写测试类Test2，分别调用类方法和实例方法，计算输出半径为5和8的圆面积和周长；以以上两个圆为底面，计算高均为8的圆柱体的表面积和体积。

Circle类代码如下：

public class Circle {
    private double r;

    public Circle() {
    }

    public Circle(double r) {
        this.r = r;
    }

    public double getR() {
        return r;
    }

    public void setR(double r) {
        this.r = r;
    }

    public double getPerimeter() {
        return 2 * Math.PI * r;
    }

    public double getArea() {
        return Math.PI * r * r;
    }

    public static double getPerimeter(double r) {
        return 2 * Math.PI * r;
    }

    public static double getArea(double r) {
        return Math.PI * r * r;
    }

    @Override
    public String toString() {
        return "Circle{" +
                "r=" + r +
                '}';
    }
}

Cylinder类代码如下：

public class Cylinder {
    private double h;
    private Circle undersurface;

    public Cylinder() {    
    }

    public Cylinder(double h, Circle undersurface) {
        this.h = h;
        this.undersurface = undersurface;
    }

    public double getH() {
        return h;
    }

    public void setH(double h) {
        this.h = h;
    }

    public Circle getUndersurface() {
        return undersurface;
    }

    public void setUndersurface(Circle undersurface) {
        this.undersurface = undersurface;
    }

    public double getSurfaceArea() {
        double circleArea = undersurface.getArea();
        double circlePerimeter = undersurface.getPerimeter();
        return 2 * circleArea + circlePerimeter * h;
    }

    public double getVolume() {
        double circleArea = undersurface.getArea();
        return circleArea * h;
    }

    @Override
    public String toString() {
        return "Cylinder{" +
                "h=" + h +
                ", undersurface=" + undersurface +
                '}';
    }
}

Test2类代码如下：

public class Test2 {
    public static void main(String[] args) {
        Circle circle1 = new Circle(5);
        System.out.println("圆1的面积是：" + circle1.getArea());
        System.out.println("圆1的周长是：" + circle1.getPerimeter());

        Circle circle2 = new Circle(8);
        System.out.println("圆2的面积是：" + Circle.getArea(circle2.getR()));
        System.out.println("圆2的周长是：" + Circle.getPerimeter(circle2.getR()));

        Cylinder cylinder = new Cylinder(8, circle1);
        System.out.println("圆柱体的表面积是：" + cylinder.getSurfaceArea());
        System.out.println("圆柱体的体积是：" + cylinder.getVolume());

        cylinder.setUndersurface(circle2);
        System.out.println("圆柱体的表面积是：" + cylinder.getSurfaceArea());
        System.out.println("圆柱体的体积是：" + cylinder.getVolume());
    }
}