= Singleton =

A singleton is a design pattern in which a class has only one instance, and
that instance is globally accessable. This is often important for use in shared
resources, such as a file, database connection, or logging application.

== Implementation ==

* Make the default constructor private, preventing other objects from using
  `new`
* Create a static creation method that acts as a constructor. This method calls
  a private constructor and instantiates a static field, which is the
  singleton. All further calls return a reference to this cached, static
  object.

== Use case ==

* strict control over global vars
* instance where a single instance of an object is required

== Cons ==

* Take special care to not instantiate several in a multithreaded enviroment