1 局部变量

#include<iostream>
using namespace std;
class Myclass
{
public:
	Myclass(int a,int b,int c);
	void GetSum();
private:
	int a,b,c;
	int Sum;//声明静态数据成员
};

// int Myclass::Sum=0;    //定义并初始化静态数据成员

Myclass::Myclass(int a,int b,int c)
{
	this->a=a;
	this->b=b;
	this->c=c;
	Sum+=a+b+c;
}

void Myclass::GetSum()
{
	std::cout<<"Sum="<<Sum<<std::endl;
}

int main()
{
	Myclass M(1,2,3);
	M.GetSum();
	Myclass N(4,5,6);
	N.GetSum();
	M.GetSum();
	return 0;
}

VS code运行结果:

[Running] cd "/home/SoftApp/VScode/CPP_Study/" && g++ main.cpp -o main && "/home/SoftApp/VScode/CPP_Study/"main
Sum=6
Sum=15
Sum=6

[Done] exited with code=0 in 0.272 seconds

2 static 静态局部变量

#include<iostream>
using namespace std;
class Myclass
{
public:
	Myclass(int a,int b,int c);
	void GetSum();
private:
	int a,b,c;
	static int Sum;//声明静态数据成员
};

// int Myclass::Sum=0;    //定义并初始化静态数据成员

Myclass::Myclass(int a,int b,int c)
{
	this->a=a;
	this->b=b;
	this->c=c;
	Sum+=a+b+c;
}
int Myclass::Sum = 0;
void Myclass::GetSum()
{
	std::cout<<"Sum="<<Sum<<std::endl;
}

int main()
{
	Myclass M(1,2,3);
	M.GetSum();
	Myclass N(4,5,6);
	N.GetSum();
	M.GetSum();
	return 0;
}

VS Code运行结果:

[Running] cd "/home/SoftApp/VScode/CPP_Study/" && g++ main.cpp -o main && "/home/SoftApp/VScode/CPP_Study/"main
Sum=6
Sum=21
Sum=21

[Done] exited with code=0 in 0.316 seconds

留意
1.增加static后,这里Sum运行后没有初始化,对所有对象共享.
2.原文介绍
- 静态全局变量不能被其它文件所用；
- 其它文件中可以定义相同名字的变量，不会发生冲突；
3.原文:Arkin:C/C++ 中的static关键字.