C++语言基础 例程 类的声明和对象的定义

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类的声明和对象的定义-形式1

#include  <iostream>#include <cstring>using namespace std;class Student{private:    int num;    char name[20];    char sex;public:    void set_data(int n, char *p,char s)    {        num=n;        strcpy(name,p);        sex=s;    }    void display( )    {        cout<<"num: "<<num<<endl;        cout<<"name: " <<name<<endl;        cout<<"sex: " <<sex<<endl<<endl;    }};int main(){    Student stud1,stud2;    stud1.set_data(1,"He",'f');    stud2.set_data(2,"She",'m');    stud1.display();    stud2.display();    return 0;}

类声明的第2种形式——更实用和常见

#include <iostream>#include <cstring>using namespace std;class Student{public:    void set_data(int n, char *p,char s);    void display( );private:    int num;    char name[20];    char sex;};void Student::set_data(int n, char *p,char s){    num=n;    strcpy(name,p);    sex=s;}void Student::display( ){    cout<<"num: "<<num<<endl;    cout<<"name: " <<name<<endl;    cout<<"sex: " <<sex<<endl<<endl;}int main(){    Student stud1,stud2;    stud1.set_data(1,"He",'f');    //stud1.sex='m';    //strcpy(stud1.name,"You");    stud2.set_data(2,"She",'m');    stud1.display();    stud2.display();    return 0;}

并非所有成员函数必须公有

#include <iostream>using namespace std;class Time{public:    void set_time( );    void show_time( );private:    bool is_time(int, int, int);    int hour;    int minute;    int sec;};void Time::set_time( ){    char c1,c2;    cout<<"请输入时间(格式hh:mm:ss)";    while(1)    {        cin>>hour>>c1>>minute>>c2>>sec;        if(c1!=':'||c2!=':')            cout<<"格式不正确，请重新输入"<<endl;        else if (!is_time(hour,minute,sec))            cout<<"时间非法，请重新输入"<<endl;        else            break;    }}void Time::show_time( ){    cout<<hour<<":"<<minute<<":"<<sec<<endl;}bool Time::is_time(int h,int m, int s){    if (h<0 ||h>24 || m<0 ||m>60 || s<0 ||s>60)        return false;    return true;}int main( ){    Time t1;    t1.set_time( );    t1.show_time( );    return 0;}