构造函数调用规则

#include<iostream>
#include<string>
using namespace std;
class Student
{
private:
    int age;
public:
    Student(int a){
        age = a;
    }
}
int main(){
    system("chcp 65001");
    Student stu1;
    system("pause");
}

#include<iostream>
#include<string>
using namespace std;
class Student
{
private:
    int age;
public:
    Student(int a){
        age = a;
    }
    void printAge(){
        cout<<age<<endl;
    }
};
int main(){
    system("chcp 65001");
    Student stu1(12);
    Student stu2(stu1);
    stu2.printAge();
    system("pause");
    return 0;
}