贺老师的教学链接  本课讲解

使用默认参数的构造函数

#include <iostream>
using namespace std;
class Time
{
public:
    Time( );
    Time(int h,int m=0,int s=0);
    void show_time( );
private:
    int hour;
    int minute;
    int sec;
};


Time::Time( )
{
    hour=0;
    minute=0;
    sec=0;
}


Time::Time(int h,int m,int s)
{
    hour=h;
    minute=m;
    sec=s;
}


void Time::show_time( )
{
    cout<<hour<<":"<<minute<<":"<<sec<<endl;
}
int main( )
{
    Time t1;
    t1.show_time();
    Time t2(8);
    t2.show_time();
    Time t3(8,30);
    t3.show_time();
    Time t4(18,56,48);
    t4.show_time();
    return 0;
}