Now that we've discussed how to choose a pattern. Imagine that
you have to write a class that can have only one
instance. So to satisfy this requirement, I would like for you
to pick one of the design patterns that we discussed in
this lesson, and write the code here that satisfies that requirement.
And when you write the code, please make sure that your
class has only one method, without counting possible constructors, and that
the class is called Singleton. And write your class right here.