实验八 类和对象

实验八类和对象（二）一、实验目的1. 进一步掌握声明类的方法，类和类的成员的概念以及定义对象的方法。

2．掌握用类和对象编制基于对象的程序。

3．掌握友元的概念、友元函数的定义与使用方法。

4．掌握静态数据成员与静态成员函数的定义与使用方法。

5．学习对多文件程序的编译和运行。

二、实验内容与结果1. 项目Exp8_1的运行结果为：0 object exist2 object exist1 object exist2. 项目Exp8_2源程序如下：#include <iostream>using namespace std;class Book{private:char bkName[20];double price;static int number;static double totalPrice;public:Book(char *,double);~Book();double getPrice(){ return price; }char * getName(){ return bkNam e; }static int getNumber(){ return number; }static double getTotalPrice(){ return totalPrice; }void display();};Book::Book(char *name,double Price) {//构造函数，可以访问静态和非静态成员strcpy(bkName,name);price=Price;number++;totalPrice+=price;}Book::~Book(){number--; //析构一本书就减少书的本数totalPrice-=price; //析构一本书就减少书的总价}//此函数仅是一个验证，表示非静态成员函数可以访问静态的数据和函数成员void Book::display(){cout<<"book name :"<<bkName<<" "<<"pirce :" <<price<<endl;cout<<"number:" <<number<<" "<<"totalPrice: "<<totalPrice<<endl;cout<<"call static f unction "<<getNumber()<<endl;}//初始化静态数据成员int Book::number=0;double Book::totalPrice=0;int main(){Book b1("C++ 程序设计",32.5);Book b2("数据库系统原理",23);cout<<b1.getName()<<"\t"<<b1.getPrice()<<endl;cout<<b2.getName()<<"\t"<<b2.getPrice()<<endl;cout<<"总共: " <<b1.getNumber() <<"\t本书"<<"\t总价：" <<b1.getTotalPrice() <<"\t元"<<endl;{Book b3("数据库系统原理",23);cout<<"总共: " <<b1.getNumber()<<"\t本书"<<"\t总价："<<b1.getTotalPrice()<<"\t元"<<endl;}//b3生存期结束cout<<"总共: " <<Book::getNumber() <<"\t本书"<<"\t总价："<<Book::getTotalPrice()<<"\t元"<<endl;b2.display();return 0;}输出结果为：C++程序设计32.5数据库系统原理23总共2本书总价：55.5 元总共3本书总价：78.5 元总共2本书总价：55.5 元book name：数据库系统原理price：23number: 2 totalPrice: 55.5call static f unction 23. 项目Exp8_3包含以下3个文件：文件Rectangle.hclass Rectangle{public:Rectangle();Rectangle(doubl e,double);double getWidth();double getHeight();void setWidth(double);void setHeight(double);double getArea();double getPerimeter();private:double width;double height;};文件Rectangle.cpp#include "Rectangle.h"Rectangle::Rectangl e(){width=1;height=1;}Rectangle::Rectangl e(double newWidth,double newHeight) {width=newWidth;height=newHeight;}double Rectangle::getWidth(){return width;}double Rectangle::getHeight(){return height;}void Rectangle::setWidth(double new Width){width=(newWidth>=0)?newWidth:0;}void Rectangle::setHeight(double newHeight){height=(newHeight>=0)?newHeight:0;}double Rectangle::getArea(){return width*height;}double Rectangle::getPerimeter (){return 2*(width+height);}文件testRectangle.cpp#include <iostream.h>#include "Rectangle.h"int main(){Rectangle rectangle1(4,40);Rectangle rectangle2(3.5,35.9);cout<<"The area of the rectangle with width "<<rectangle1.getWidth()<<" and height "<<rectangle1.getHeight()<<" is "<<rectangle1.getArea()<<endl;cout<<"The perimeter of the rectangl e with width "<<rectangle1.getWidth()<<" and height "<<rectangle1.getHeight()<<" is "<<rectangle1.getPerimeter()<<endl;cout<<"The area of the rectangle with width "<<rectangle2.getWidth()<<" and height "<<rectangle2.getHeight()<<" is "<<rectangle2.getArea()<<endl;cout<<"The perimeter of the rectangl e with width "<<rectangle2.getWidth()<<" and height "<<rectangle2.getHeight()<<" is "<<rectangle2.getPerimeter()<<endl;return 0;}输出结果为：The area of the rectangle with width 4 and height 40 is 160The perimeter of the rectangle with width 4 and height 40 is 88The area of the rectangle with width 3.5 and height 35.9 is 125.65The perimeter of the rectangle with width 3.5 and height 35.9 is 78.8运行结果与实验六第1题相同。

4. 项目Exp8_4包含3个文件：Rectangle.h、Rectangle.cpp和testRectangle.cpp，其中Rectangle.cpp与项目Exp7_2中的文件相同，另外两个文件作如下修改：文件Rectangle.hclass Rectangle{public:Rectangle();Rectangle(doubl e,double);double getWidth();double getHeight();void setWidth(double);void setHeight(double);double getArea();double getPerimeter();friend void print_Rectangle(Rect angle); private:double width;double height;};文件testRectangle.cpp#include "Rectangle.h"#include <iostream.h>void print_Rectangle(Rectangl e rec){cout<<rec.width<<endl;cout<<rec.height<<endl;}main(){Rectangle rec1;print_Rectangle(rec1);Rectangle rec2(3,5);print_Rectangle(rec2);}输出结果为：1135。