C++单例模式

#include<iostream>using namespace std;class Singleton{public:static Singleton& instance(){return s;};//返回一个引用而不是指针，是因为用户可能不小心删除指针 int getValue(){return i;};void setValue(int x){i=x;}; private:static Singleton s;int i;Singleton(int x):i(x){};//不允许构造函数 Singleton& operator=(Singleton&);//不允许赋值 Singleton(const Singleton&); //不允许拷贝};Singleton Singleton::s(47);int main(){Singleton &s=Singleton::instance();cout<<s.getValue()<<endl;Singleton &s2=Singleton::instance();s2.setValue(9);cout<<s.getValue()<<endl;return 0;}