类和对象——实验二

类和对象——实验二

作者：miaomiao

题出自某高校实验作业题

一、实验内容

定义一个 圆类(Circle) ,要求用两种方法定义：

方法1：要求属性为半径，操作为计算圆的周长和面积。

方法2：要求属性为半径( radius )、圆周长和面积，操作为输出半径、周长和面积。

要求定义构造函数（以半径为参数，缺省值为0，周长和面积在构造函数中生成）和复制构造函数。

二、解答

方法1：

定义类的代码

class Circle {
private:
    double radius;
public:
    Circle(double r);
    ~Circle() {};
    void Area();
    void Perimeter();
};

类中成员函数的实现

Circle::Circle(double r) {
    radius = r;
}
void Circle::Area() {
    cout << "面积 = " << PI * radius*radius << endl;
}
void Circle::Perimeter() {
    cout << "周长 = " << 2 * PI*radius << endl;
}

完整程序

#include<iostream>
#include<iomanip>
using namespace std;
const double PI = 3.1415;	//定义一个常量

class Circle {
private:
    double radius;
public:
    Circle(double r);
    void Area();
    void Perimeter();
};

Circle::Circle(double r) {
    radius = r;
}

void Circle::Area() {
    cout << "面积 = " << PI * radius*radius << endl;
}

void Circle::Perimeter() {
    cout << "周长 = " << 2 * PI*radius << endl;
}

int main() {
    Circle cir1(10.5);

    cout << fixed << setprecision(3);	//iomanip库函数，作用使输出保留3位小数
    cir1.Area(); cir1.Perimeter();
    cout.unsetf(ios_base::fixed);	//关闭3位小数的显示要求
    return 0;
}

方法2：

定义类的代码

class Circle {
private:
    double radius, area, perimeter;
public:
    Circle(double r = 0);
    Circle(Circle &c);
    void Show();
};

类中成员函数的实现

Circle::Circle(double r) {
    radius = r;
    area = PI * r*r;
    perimeter = 2 * PI*r;
}
Circle::Circle(Circle &c) {
    radius = c.radius;
    area = c.area;
    perimeter = c.perimeter;
}
void Circle::Show() {
    cout << fixed << setprecision(3) << "半径 = " << radius << ", 面积 = " << area << ", 周长 = " << perimeter << endl;
}

完整程序

#include<iostream>
#include<iomanip>
using namespace std;

const double PI = 3.1415;

class Circle {
private:
    double radius, area, perimeter;
public:
    Circle(double r = 0);
    Circle(Circle &c);
    void Show();
};

Circle::Circle(double r) {
    radius = r;
    area = PI * r*r;
    perimeter = 2 * PI*r;
}

Circle::Circle(Circle &c) {
    radius = c.radius;
    area = c.area;
    perimeter = c.perimeter;
}

void Circle::Show() {
    cout << fixed << setprecision(3) << "半径 = " << radius << ", 面积 = " << area << ", 周长 = " << perimeter << endl;
}

int main() {
    Circle cir(10.5);
    cir.Show();

    Circle cir1(cir);
    cir1.Show();

    return 0;
}