(1）声明Point（点）类，由Point类派生出Circle（圆）类，再由Circle类派生出Cylinder(圆柱体)类。将类的定义部分分别作为3个头文件，对它们的成员函数的声明部分分别作为3个源文件(.cpp文件)，在主函数中用#include命令把它们包含进来，形

Point.h头文件定义：

#ifndef POINT_H
#define POINT_H

class Point {
public:
    Point(double x = 0, double y = 0);
    double getX() const;
    double getY() const;
    void setX(double x);
    void setY(double y);
private:
    double x;
    double y;
};

#endif

Point.cpp源文件实现：

#include "Point.h"

Point::Point(double x, double y) {
    this->x = x;
    this->y = y;
}

double Point::getX() const {
    return x;
}

double Point::getY() const {
    return y;
}

void Point::setX(double x) {
    this->x = x;
}

void Point::setY(double y) {
    this->y = y;
}

Circle.h头文件定义：

#ifndef CIRCLE_H
#define CIRCLE_H

#include "Point.h"

class Circle : public Point {
public:
    Circle(double x = 0, double y = 0, double r = 0);
    double getR() const;
    void setR(double r);
    double area() const;
private:
    double r;
};

#endif

Circle.cpp源文件实现：

#include "Circle.h"
#include <cmath>

Circle::Circle(double x, double y, double r) : Point(x, y) {
    this->r = r;
}

double Circle::getR() const {
    return r;
}

void Circle::setR(double r) {
    this->r = r;
}

double Circle::area() const {
    return M_PI * r * r;
}

Cylinder.h头文件定义：

#ifndef CYLINDER_H
#define CYLINDER_H

#include "Circle.h"

class Cylinder : public Circle {
public:
    Cylinder(double x = 0, double y = 0, double r = 0, double h = 0);
    double getH() const;
    void setH(double h);
    double volume() const;
private:
    double h;
};

#endif

Cylinder.cpp源文件实现：

#include "Cylinder.h"
#include <cmath>

Cylinder::Cylinder(double x, double y, double r, double h) : Circle(x, y, r) {
    this->h = h;
}

double Cylinder::getH() const {
    return h;
}

void Cylinder::setH(double h) {
    this->h = h;
}

double Cylinder::volume() const {
    return area() * h;
}

主函数中的头文件包含：

#include "Point.h"
#include "Circle.h"
#include "Cylinder.h"