面向?qū)ο髮?shí)驗(yàn)二友元

面向?qū)ο髮?shí)驗(yàn)二友元一、 實(shí)驗(yàn)?zāi)康囊粋€(gè)類的友元函數(shù)能夠直接訪問該類所有成員，包括public、protected、private類型的成員；一個(gè)類可以是另一個(gè)類的友元，友元類的所有成員函數(shù)都是另一個(gè)類的友元函數(shù)，能夠直接訪問另一個(gè)類的所有成員。本實(shí)驗(yàn)?zāi)康氖牵菏炀氄莆沼言瘮?shù)的設(shè)計(jì)與應(yīng)用；熟練掌握友元類的設(shè)計(jì)與應(yīng)用。二、 實(shí)驗(yàn)內(nèi)容使用VisualC++6.0分別建立學(xué)生類CStudent、學(xué)生類的友元函數(shù)以及學(xué)生類的友元類，并編制主程序來驗(yàn)證對所創(chuàng)建的友元函數(shù)和友元類的正確性。三、 實(shí)驗(yàn)要求1.設(shè)計(jì)一個(gè)學(xué)生類CStudents，其結(jié)構(gòu)如下：私有數(shù)據(jù)成員ID(學(xué)號)、Name(學(xué)生姓名)、Score(成績)；構(gòu)造函數(shù)對數(shù)據(jù)成員初始化；設(shè)計(jì)一個(gè)友元函數(shù)Display(CStudent&)；根據(jù)百分制成績輸出成績的等級：>=90為優(yōu)秀；80?89為良好；70?79為中等；60?69為及格；<60為不及格；輸出結(jié)果如下：姓名成績等級LeBronJams75中等MichaelJordan98優(yōu)秀ChrisBosh55不及格StephenCurry80良好2.設(shè)計(jì)一個(gè)CStudents的友元類CTeacher，其結(jié)構(gòu)包含兩個(gè)成員函數(shù)：voidModify(CStudent&s)：實(shí)現(xiàn)對學(xué)生的成績的修改；voidDisplay(CStudent&s)輸出s成績的等級；四、 思考題友元函數(shù)有什么特點(diǎn)？在什么時(shí)候采用友元函數(shù)？友元類有什么特點(diǎn)？什么是使用友元類的限制？實(shí)驗(yàn)代碼：//CStudents.h#ifndefCSTUDENTS_H_#defineCSTUDENTS_H_#include<iostream>#include<string>usingnamespacestd;classCStudents{friendclassCTeacher;private:intID;//學(xué)號stringName;//姓名intScore;//成績public:CStudents(inti=0,char*n="null",intS=0);//t構(gòu)造函數(shù)初始化friendvoidDisplay(CStudents&s);};classCTeacher{public:CTeacher(){CStudents();}voidModify(CStudents&s);//實(shí)現(xiàn)對學(xué)生成績的修改voidDisplay(CStudents&s);〃輸出s成績的等級};#endif//CStudents.cpp#include<iostream>#include"CStudents.h"usingnamespacestd;CStudents::CStudents(inti,char*n,intS):ID(i),Name(n),Score(S){}voidDisplay(CStudents&s){cout.width(15);cout<<s.Name;cout.width(8);cout<<s.Score;if(s.Score>=90){cout.width(10);cout<<"優(yōu)秀"<<endl;}elseif(s.Score>=80&&s.Score<=89){cout.width(10);cout<<"良好"<<endl;elseif(s.Score>=70&&s.Score<=79){cout.width(10);cout<<"中等"<<endl;}elseif(s.Score>=60&&s.Score<=69){cout.width(10);cout<<"及格"<<endl;}else{cout.width(10);cout<<"不及格"<<endl;}}voidCTeacher::Modify(CStudents&s){stringg;cout<<"pleaseenterwhatdatayouwanttochange(取消toquit):(成績、學(xué)號、姓名);;while(1){cin>>g;if(g==”取消”){break;}elseif(g=="成績"){cout<<"Howmanyyouwanttochange:";intcheng;cin>>cheng;s.Score=cheng;}elseif(g=="學(xué)號”){cout<<"WhatIDyouwanttochange:";intji;cin>>ji;s.ID=ji;}elseif(g=="姓名”)cout<<"Whatnameyouwanttochange:";stringname;cin>>name;s.Name=name;}elsecout<<"youenteriswrong!";cout<<"pleaseenterwhatdatayouwanttochange(取消toquit):(成績、學(xué)號、姓名)”；}}voidCTeacher::Display(CStudents&s){if(s.Score>=90){cout.width(10);cout<<"優(yōu)秀"<<endl;}elseif(s.Score>=80&&s.Score<=89){cout.width(10);cout<<"良好"<<endl;}elseif(s.Score>=70&&s.Score<=79){cout.width(10);cout<<"中等"<<endl;}elseif(s.Score>=60&&s.Score<=69){cout.width(10);cout<<"及格"<<endl;}else{cout.width(10);cout<<"不及格"<<endl;//user.cpp#include"CStudents.h"http://#include<iostream>//usingnamespacestd;intmain(){CStudentsa2(1400830222,"LeBronJams",75);CStudentsa1;CStudentsa3(1400830221,"MichaelJordan",98);CStudentsa4(1400830220,"ChrisBosh",55);CStudentsa5(1400830219,"StephenCurrt",80);cout<<" 姓名成績等級"<<endl;cout<<" "<<endl;Display(a1);Display(a2);Display(a3);Display(a4);Display(a5);CTeacherb1;cout<<""<<endl;cout<<""<<endl;cout<<"測試CTeacher的Display."<<endl;b1.Display(a4);cout<<""<<endl;cout<<""<<endl;b1.Modify(a2);Display(a2);return0;}思考題1：友元函數(shù)有什么特點(diǎn)？在什么時(shí)候采用友元函數(shù)？答：友元函數(shù)不屬于類的內(nèi)部函數(shù)，但卻可以訪問類的私有成員。在想實(shí)現(xiàn)數(shù)據(jù)之間的共享和減少資源開銷時(shí)可以使