多态性与虚函数

一、实验目的和要求

1. 2. 3. 4.

了解多态的概念；

了解虚函数的作用及使用方法；

了解静态关联和动态关联的概念和用法； 了解纯虚函数和抽象类的概念和用法

二、实验内容和结果

1. 声明一个车（vehicle）基类，具有MaxSpeed、weight等成员变量有Run、Stop等成员

函数，由此派生出自行车（bicycle）类、汽车（motorcar）类，自行车（bicycle）类有高度（Height）等属性，汽车（motorcar）有座位数（SeatNum）等属性，类从bicycle和motorcar派生出摩托车（motorcycle）类，它们都有Run、Stop等成员函数，使用虚函数完成。（各个类都必须定义构造函数和析构函数）

#include usingnamespace std; class vehicle {

protected: float MaxSpeed; float weight; public: ~vehicle(){}

vehicle(float m,float w):MaxSpeed(m),weight(w){} virtualvoid Run () {

cout<<\"车已经启动啦！！！\"<}

virtualvoid Stop () {

cout<<\"vehicle已经停啦！！！\"<class bicycle: virtualpublic vehicle {

protected: float Height; public: ~bicycle(){}

bicycle(float m,float w,float h):vehicle( m,w),Height(h){} void Run () {

cout<<\"The height of bicycle is:\"<void Stop () {

cout<<\"bicycle已经停啦！！！\"<} };

class motorcar: virtualpublic vehicle {

protected: int SeatNum; public: ~motorcar(){}

motorcar(float m,float w,float s):vehicle( m,w),SeatNum(s){} void Run () {

cout<<\"The number of motorcar's seat is:\"<void Stop () {

cout<<\"motorcar已经停啦！！！\"<class motorcycle: public bicycle, public motorcar

{ public:

~motorcycle(){}

motorcycle(float m,float w,float h,float s):vehicle( m,w),bicycle( m,w,h), motorcar(m,w,s){} void Run () {

cout<<\"MaxSpeed:\"<cout<<\"The number of seat is:\"<void Stop () {

cout<<\"motorcycle已经停啦！！！\"<int main() {

vehicle a(108,53); bicycle b(180,50,2); motorcar c(180,80,5);

motorcycle d(120,90,1.2,3); vehicle *p[4]={&a,&b,&c,&d }; for(int i=0;i<4;i++) {

p[i]->Stop(); p[i]->Run(); }

return 0; }

2. 定义抽象基类Shape，由它派生出3个派生类：Circle，Square，Rectangle，Triangle，

Trapezoid（梯形）。用一个函数printArea分别输出以上五者的面积，5个图形的数据在定义对象时给出。

#include #include usingnamespace std; class Shape

{ public: ~Shape(){}

virtualvoid Setdata(float=0 ,float=0 ,float=0) =0; virtualfloat Area() =0;//求面积、纯虚函数 };

class Triangle:public Shape //三角形类 {

protected: float W,H; public:

~Triangle(){}

Triangle(float w=0,float h=0):W(w),H(h){} void Setdata(float w=0,float h=0,float j=0) { W=w; H=h; }

float Area() {

return W*H/2; }

};

class Square:public Shape //正方形类 {

protected: float S; public: ~Square(){}

Square(float s=0):S(s){}

void Setdata(float s=0,float h=0,float { S=s; }

float Area() {

return S*S; } };

class Rectangle:public Shape //矩形类 {

protected: float L; float W;

=0) jpublic: ~Rectangle(){}

void Setdata(float l=0,float w=0,float j=0) { L=l; W=w; }

Rectangle(float l=0,float w=0):L(l),W(w){} float Area() {

return L*W; } };

class Circle:public Shape //圆类 {

protected: float R; public: ~Circle(){}

Circle(float r=0):R(r){}

void Setdata(float r=0,float h=0,float j=0) {

R=r; } float Area() {

return 3.1415926*R*R; } };

class Trapezoid:public Shape //梯形类 {

protected: float SD; float XD; float H; public: ~Trapezoid(){}

Trapezoid(float sd=0,float xd=0,floath=0):SD(sd),XD(xd),H(h){}

void Setdata(float sd=0,float xd=0,float { SD=sd; XD=xd; H=h;

=0) h }

float Area() {

return 0.5*(SD+XD)*H; } };

int main() {

cout<sjx.Setdata(2,3); //设置数据 cout<<\"三角形面积为：\"<cout<<\"正方形面积为：\"<cout<<\"矩形面积为：\"<cout<<\"圆面积为：\"<tx.Setdata(1,2,3); //设置数据 cout<<\"梯形面积为：\"<float area=0; for(int i=0;i<5;i++) area+=p[i]->Area();

cout<<\"总面积为：\"<3. 实现计算器程序，要求输入两个数和运算符，得到结果，用简单工厂模式完成。

#include usingnamespace std; class Operater {

protected: int a,b,result; char op; public:

Operater(int A,char OP,int B):a(A),b(B),op(OP) {} Operater() {

a=1,b=1,op=' '; }

virtualint getResult()=0; };

class OperaterAdd:public Operater { public:

OperaterAdd(int A,char OP,int B):Operater(A,OP,B) OperaterAdd():Operater() {} int getResult() {return result=a+b;} };

class OperaterSub:public Operater {public: OperaterSub(int A,char OP,int B):Operater(A,OP,B) {} OperaterSub():Operater() {} int getResult() {

return result=a-b; } };

class OperaterMul:public Operater

{} {

public: OperaterMul(int A,char OP,int B):Operater(A,OP,B) {} OperaterMul():Operater() {} int getResult() {return result=a*b;}};

class OperaterDiv:public Operater { public:

OperaterDiv(int A,char OP,int B):Operater(A,OP,B) {}

OperaterDiv():Operater() {} int getResult() {

if(b!=0) {

result=a/b; return result; }

else cout<<\"除数不能为0！\"; } };

class OperaterFactory {

public: Operater *createOperate(char op) { Operater *oper; switch(op)

{case'+': oper=new OperaterAdd();break; case'-': oper=new OperaterSub();break; case'*': oper=new OperaterMul();break; case'/': oper=new OperaterDiv();break; }

return oper; } };

int main()

{ OperaterFactory OF;

Operater *oper=OF.createOperate('+'); cout<getResult()<