The Singleton is the most hated design pattern in the (rather limited) history of design patterns. Just stating that, however, doesn’t mean you shouldn’t use the singleton: a toilet brush is not the most pleasant device either, but sometimes it’s simply necessary.
The Singleton design pattern grew out of a very simple idea that you should only have one instance of a particular component in your application. For example, a component that loads a database into memory and offers a read-only interface is a prime candidate for a Singleton, since it really doesn’t make sense to waste memory ...
