C++ Static使用

#include
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="< 
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
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="< 
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
 
3 简化观察 
#include
using namespace std;

void fn(){ 
	static int n=-1;
	n++; 
	cout< 
[Running] cd "/home/SoftApp/VScode/CPP_Study/" && g++ main.cpp -o main && "/home/SoftApp/VScode/CPP_Study/"main
0
1
2

[Done] exited with code=0 in 0.258 seconds
 
#include
using namespace std;

void fn(){ 
	int n=-1;
	n++; 
	cout< 
[Running] cd "/home/SoftApp/VScode/CPP_Study/" && g++ main.cpp -o main && "/home/SoftApp/VScode/CPP_Study/"main
0
0
0

[Done] exited with code=0 in 0.247 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.