设计模式——单例模式

#include <stdio.h>      /* printf */
class Singletest
{
public:
    static Singletest* getinstace();
    ~Singletest();

private:
    Singletest(); 
static Singletest* instance; 
};

Singletest* Singletest::instance = NULL;
Singletest* Singletest::getinstace()
{
if (instance == NULL)
{
instance = new Singletest();
printf("instance = %x\n",instance);
printf("222222222222222222222222  \n");
}
return instance;
}
Singletest::Singletest()
{
printf("11111111111111111111111  \n");
}
Singletest::~Singletest()
{
instance = NULL;
printf("3333333333333333333333333 \n");
}
int main ()
{
  Singletest* test1 = Singletest::getinstace();
  Singletest* test2 = Singletest::getinstace();
  printf("test1 = %x,test2 = %x\n",test1,test2);
  if (Singletest::getinstace())
  { 
 delete Singletest::getinstace();
  }
  Singletest* test3 = Singletest::getinstace();
  if (Singletest::getinstace())
  { 
 delete Singletest::getinstace();
  }
  printf("test3 = %x",test3);
  test2 = NULL;
  test1 = NULL;
  test3 = NULL;
  return 0;
}