<pre name="code" class="cpp">
#include<iostream>
#include<string>
using namespace std;

class Student{
private:
	string name;
	int age;
	float score;
	static int number; //定义静态成员变量
	static float total;
public:
	Student(string name,int age,float score);
	Student(const Student & s);
	~Student();
	void setName(string n);
	string getName();
	void setAge(int a);
	int getAge();
	void setScore(float s);
	float getScore();
	void say();
	static float getAverage();
};
/*注意。假设构造函数的形參和 类的成员变量名字一样。必须採用 this -> name = name ,而不能够 写成 name = name*/
Student::Student(string name,int age,float score){
	this->name = name;
	this ->age = age;
	this ->score = score;
	number++;
	total += score;
}

Student::Student(const Student & s){
	this ->name = s.name;
	this ->age = s.age;
	this ->score = s.score;
}

Student::~Student(){}
string Student::getName(){
	return this->name;
}
int Student::getAge(){
	return this->age;
}
float Student::getScore(){
	return this ->score;
}

void Student::setName(string n){
	this ->name = n;
}

void Student::setAge(int a){
	this ->age =a ;
}

void Student::setScore(float s){
	this->score =s;
}

void Student::say(){
	cout << this->name <<" : " << this->age <<" : " << this ->score << " : " << Student::number <<endl;
}

float Student::getAverage(){
	if(number == 0)
	{
		return 0;
	}
	else
		return total/number;
}
//静态变量必须初始化。才干够使用
int Student::number = 0;
float Student::total = 0;

int main(int argc,char*argv[])
{
	//即使没有创建对象也能够訪问静态成员方法
	cout << "没有学生的时候的平均成绩"<< Student::getAverage() <<endl;
	
	Student s1("lixiaolong",32,100.0);
	Student s2("chenglong",32,95.0);
	Student s3("shixiaolong",32,87.0);
	s1.say();
	s2.say();
	s3.say();
	cout << "平均成绩为" << Student::getAverage() <<endl;
	system("pause");
	return 0;
}