C++类静态成员变量和const常量的初始化方法

#include <iostream>
#include <string>
#include <cstdio>
#include <cstring>

using namespace std;
class A{
public:
static void fun()
{
ab = 2;
cout << ab << endl;
}
private:
static int ab;
};

int A::ab = 10//在此初始化

int main(int argc, char *argv[])
{
A::fun();
return 0;
}

#include <iostream>
#include <string>
#include <cstdio>
#include <cstring>

using namespace std;
class A{
public:
A:ab(10)//在此初始化ab
{ ;}
static void fun()
{
ab = 2;
cout << ab << endl;
}
const int ab;

};