单实例模式1

#include <iostream>
using namespace std;

class Singleton {
public:
    static Singleton *getInstance()
    {
        if (instance == 0)
            instance = new Singleton();
        return instance;
    }

    void printHello()
    {
        cout << "Hello" << endl;
    }

private:
    static Singleton *instance;
    Singleton() {cout << "Init a instance" << endl;}
};

Singleton* Singleton::instance = 0;

int
main(void)
{
    int i;
    for (i = 0; i < 10; i++)
        Singleton::getInstance()->printHello();

    return 0;
}

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