Lazy initialization:

In a software design pattern view, lazy initialization is often used together with a factory method pattern. This combines three ideas:

• using a factory method to get instances of a class (factory method pattern)
• storing the instances in a map, so you get the same instance the next time you ask for an instance with same parameter (Multiton pattern, similar to the singleton pattern)
• using lazy initialization to instantiate the object the first time it is requested (lazy initialization pattern).