设计模式--单例模式

#include<iostream>
using namespace std;

class Singleton
{
public:
    static Singleton * Instance();
protected:
    Singleton();
private:
    static Singleton * _instance;
};

Singleton * Singleton::_instance = 0;
Singleton::Singleton()
{
    cout << "Singleton..." << endl;
}
Singleton *Singleton::Instance()
{
    cout << "Instance..." << endl;
    if(_instance == 0)
    {
        _instance = new Singleton();
    }
    return _instance;
}

int main()
{
    Singleton *sgn = Singleton::Instance();
     return 0;
}