单例模式（懒汉模式/饿汉模式）

相关概念参考：【C++】C++ 单例模式总结（5种单例实现方法）_单例模式c++实现-CSDN博客

#include<iostream>class LazySingle{
public:static LazySingle& getInstance(){static LazySingle instance;return instance;}void hello(){std::cout<<"Congratulations"<<std::endl;}private:LazySingle(){};
};
class LazySinglePtr{public:static LazySinglePtr* getInstance(){static LazySinglePtr instance;return &instance;}void hello(){std::cout<<"Congratulations"<<std::endl;}private:LazySinglePtr(){};
};class HungrySingle{
public:static HungrySingle& getInstance(){return instance_;}private:static HungrySingle instance_;HungrySingle(){};
};HungrySingle  HungrySingle::instance_;int main(){std::cout<<"懒汉引用模式:"<<std::endl;auto& lazy1=LazySingle::getInstance();LazySingle& lazy2=LazySingle::getInstance();std::cout<<" lzay1="<<&lazy1<<" lzay2="<<&lazy2<<" instance="<<&LazySingle::getInstance()<<std::endl;lazy1.hello();std::cout<<"懒汉指针模式:"<<std::endl;auto lazyptr1=LazySinglePtr::getInstance();LazySinglePtr* lazyptr2=LazySinglePtr::getInstance();std::cout<<" lzay1="<<lazyptr1<<" lzay2="<<lazyptr2<<" instance="<<LazySinglePtr::getInstance()<<std::endl;lazyptr1->hello();std::cout<<"饿汉模式:"<<std::endl;HungrySingle& hungry1=HungrySingle::getInstance();HungrySingle& hungry2=HungrySingle::getInstance();std::cout<<" hungry1="<<&hungry1<<" hungry2="<<&hungry2<<" instance="<<&HungrySingle::getInstance()<<std::endl;return 0;}

输出：

懒汉引用模式:lzay1=0x7ff61a279e90 lzay2=0x7ff61a279e90 instance=0x7ff61a279e90
Congratulations
懒汉指针模式:lzay1=0x7ff61a279ee0 lzay2=0x7ff61a279ee0 instance=0x7ff61a279ee0
Congratulations
饿汉模式:hungry1=0x7ff61a2aa030 hungry2=0x7ff61a2aa030 instance=0x7ff61a2aa030