懒汉模式

class Singleton{
public:
    static Singleton& getInstance(){
        static Singleton instance;
        return instance;
    }
    Singleton(const Singleton&)=delete;
    Singleton& operator = (const Singleton&)=delete;
private:
    Singleton(){}
    ~Singleton(){}
};

饿汉模式

class Singleton{
public:
    static Singleton& getInstance(){
        return instance;
    }
    Singleton(const Singleton&)=delete;
    Singleton& operator = (const Singleton&)=delete;
private:
    Singleton(){}
    ~Singleton(){}
    static Singleton instance;
};
Singleton Singleton::instance;