小朋友学C++（16）：C++创建对象的3种方式

#include <iostream>
using namespace std;
class A
{
private:
    int n;
public:
    A(int m)
    {
        n = m;
        cout << "Constructor method is invoked!" << endl;   
    }
    void printNum()
    {
        cout << "n = " << n << endl;
    }
};
int main()
{
    // 第一种 
    A a1(1);            // a1在栈中 
    a1.printNum();
    // 第二种 
    A a2 = A(2);        // a2在栈中 
    a2.printNum();
    // 第三种 
    A *a3 = new A(3);   // a3所指的对象在堆中，但是a3本身放在栈中 
    a3->printNum();
    delete a3;
       return 0;
}

Constructor method is invoked!
n = 1
Constructor method is invoked!
n = 2
Constructor method is invoked!
n = 3