单件模式确保一个类只有一个实例，并提供一个全局访问点。

确定在性能和资源上的限制，然后小心地选择适当的方案来实现单件，以解决多线程的问题。

代码链接：

单件模式类图：

源代码：

 

#ifndef CHOCOLATEBOILER_H#define CHOCOLATEBOILER_H#include
    
     class ChocolateBoiler{    private:        ChocolateBoiler()        {            empty = true;            boiled = false;        }        ~ChocolateBoiler()        {            uniqueInstance = 0;        }        ChocolateBoiler( const ChocolateBoiler& );        void operator=( const ChocolateBoiler& );    public:        static ChocolateBoiler * getInstance()        {            if(uniqueInstance==0)            {                std::cout << "Creating unique instance of Chocolate Boiler" << std::endl;                uniqueInstance = new ChocolateBoiler();            }            std::cout << "Returning instance of Chocolate Boiler"<< std::endl;            return uniqueInstance;        }        void fill()        {            if(isEmpty())            {                empty = false;                boiled =false;            }        }        void drain()        {            if(!isEmpty() && isBoiled())            {                empty = true;            }        }        void boil()        {            if(!isEmpty() && !isBoiled())            {                boiled = true;            }        }        bool isEmpty()        {            return empty;        }        bool isBoiled()        {            return boiled;        }    protected:    private:        bool empty;        bool boiled;        static ChocolateBoiler* uniqueInstance;};#endif // CHOCOLATEBOILER_H
    

测试代码：

 

 

#include "ChocolateBoiler.h"ChocolateBoiler* ChocolateBoiler::uniqueInstance = 0;int main(){    ChocolateBoiler* boiler = ChocolateBoiler::getInstance();    boiler->fill();    boiler->boil();    boiler->drain();    ChocolateBoiler *boiler2= ChocolateBoiler::getInstance();    if(boiler == boiler2)        std::cout<<"Got same boiler"<

 

测试结果如下：