C++操作题-定义一个Cat类体会静态数据成员和静态成员函数的用法

一、问题描述

【问题描述】定义一个Cat类，拥有数据成员itsAge记载Cat的年龄；静态数据成员HowManyCats，记录Cat的个体数目；静态成员函数GetHowMany（），存取HowManyCats。设计程序测试这个类，体会静态数据成员和静态成员函数的用法。

【输入形式】无
【输出形式】
【样例输入】无
【样例输出】

    Cat1age=1

    There are 1 cats alive!

    Cat2age=2

    There are 2 cats alive!

    Cat3age=3

    There are 3 cats alive!

    Cat4age=4

    There are 4 cats alive!

    Cat5age=5

    There are 5 cats alive!

    There are 4 cats alive!

    There are 3 cats alive!

    There are 2 cats alive!

    There are 1 cats alive!

    There are 0 cats alive!

二、代码实现

#include<iostream>
using namespace std;

class Cat
{
    private:
        int itsAge;
        static int HowManyCats;//静态数据成员，类内定义，类外声明
    public:
    //静态成员函数，可在类体内定义，也可在类体内声明类体外定义
        static int GetHowMany()
        {
            return HowManyCats;
        }
      
        Cat(int itsAge);
        ~Cat();
};
int Cat::HowManyCats=0;
Cat::Cat(int itsAge)
{
    this->itsAge=itsAge;
    ++HowManyCats;
    cout<<"There are "<<HowManyCats<<" cats alive!"<<endl;
}
Cat::~Cat()
{
    --HowManyCats;
    cout<<"There are "<<HowManyCats<<" cats alive!"<<endl;

}
int main()
{
    cout<<"Cat1age=1"<<endl;
    Cat c1(1);
    cout<<"Cat2age=2"<<endl;
    Cat c2(2);
    cout<<"Cat3age=3"<<endl;
    Cat c3(3);
    cout<<"Cat4age=4"<<endl;
    Cat c4(4);
    cout<<"Cat5age=5"<<endl;
    Cat c5(5);
    return 0;
}