C++中构造函数初始化列表

#include <iostream>
using namespace std;

class A
{
public:
int a;

public:
A()
:a(0)
{}

A(int x)
:a(x)
{}
};

int main()
{
A obj0;
A obj1(1);
cout << obj0.a << endl;
cout << obj1.a << endl;

return 0;
}