#include <iostream>
#include <thread>
#include <mutex>
using namespace std;

class singleton
{
  private:
    static int count;
    static singleton *instance; // this instace is created as static as it will crete only once and all the objects 
                                // which are created will use only this instance
    static mutex m;
    singleton() //default constrcutor// these all are kept in private to avoid creation of objects
    {
      count++;
      cout<<"Instance has been created : "<<count<<" time"<<endl;
    }
    singleton(const singleton &s); //copy constructor to keep in private in oder to avoid copying the object as it can create as default
    singleton operator=(const singleton &s); //similar with the assignment operator

  public:
    void print(string msg)
    {
       cout<<msg<<endl;
    }
  
    static singleton* getinstance() // this is static member fuction created to access the static data members and return the instace
    {
      if(instance == nullptr)
      {     
       m.lock();
       if(instance == nullptr)
       {
           instance = new singleton();
       }
       m.unlock();
      }
      return instance;
    }


};
 
int singleton::count =0;
singleton* singleton::instance=nullptr;
mutex singleton::m;

void funcinst1()
{
   singleton *s1 = singleton::getinstance();
   s1->print("s1 instance is created");  
}

void funcinst2()
{
   singleton *s2 = singleton::getinstance();
   s2->print("s2 instance is created");
}


int main() {

   thread t1(funcinst1); 
   thread t2(funcinst2);

   t1.join();
   t2.join();
   
}