C++类const成员变量声明和构造函数中都可以赋值，都存在时最终构造函数中的值生效

#include <iostream>
using namespace std;

class Test {
public:
    Test() : num(5) {}
    void Print()
    {
        cout << "num is " << num << endl;
    }
public:
    const int num = 10;
};



int main() {
    cout << "hello lddgo.net" << endl;
    Test a;
    a.Print();
    return 0;
}

输出如下：

hello lddgo.net

num is 5