class Demo
{
public:
    Demo(){}
    Demo(string name, int age){
           m_strName = name;
           m_iAge = age;
    }                            //构造函数可以重载

private:
    string m_strName;
    int m_iAge;
};

class Demo
{
public:
    Demo(){}
    Demo(string name = "James", int age = 24){
           m_strName = name;
           m_iAge = age;
    }                        //构造函数形参列表可以赋初值，但这种情况不行，全部赋初值会与前面的无参构造函数冲突

private:
    string m_strName;
    int m_iAge;
};

class Demo
{
public:
    Demo(){}
    Demo(string name, int age)：m_strName(name),m_iAge(age){}    //初始化列表,可用于初始化const修饰的
                                                                //成员变量，初始化列表先于构造函数执行，效率高
private:
    const string m_strName;
    const int m_iAge;
};