In simplest terms, what is a factory?

Question

What is a factory and why would I want to use one?

Answer 1

The factory is an object, that creates objects. The common usage includes two cases:

• When you want to delegate the choice of the concrete object to the factory - e.g. it may return an already existing object (see Integer.valueOf(), which is a so-called factory method) or choose a concrete implementation depending on some conditions - e.g. supplied argument or pre-defined options (see XPathFactory class in Java API for XML Processing)
• When you want more flexibility for some universal job. You cannot pass a method or a constructor as an argument (well, you can, but reflection sucks), so you use a concrete factory as an object source (e.g. SomeFactory in a generic method).