Conclusion

It is often necessary to enforce a single instantiation for a particular object. This chapter has shown two very different techniques. SINGLETON makes use of private constructors, a static variable, and a static function to control and limit instantiation. MONOSTATE simply makes all variables of the object static.

SINGLETON is best used when you have an existing class that you want to constrain through derivation and don't mind that everyone will have to call the Instance() method to gain access. MONOSTATE is best used when you want the singular nature of the class to be transparent to the users or when you want to use polymorphic derivatives of the single object.