SE450: Creational Patterns: Static Factory [6/12]

Normally, how do you create an instance of a class?

However, you can write your own method to instantiate a class. This is not one of the GoF patterns, but is documented in Joshua Bloch's Effective Java.
Benefits: Static Factory methods...

• Have names
• Aren't required to create a new object each time they are invoked
• They can return of object of any subtype of their return type.

Disadvantages:

• Classes without public or protected constructors can't be subclassed (this can be a blessing in disguise as it forces programmers to use composition over inheritance)
• Static Factory methods don't stand out from other static methods. This is especially annoying when looking through JavaDoc, since the constructors all get their own section. Get around this by using conventions.

Convention:

• valueOf Returns an instance that has, loosely speaking, the same value as its parameters. Basically, it is a type conversion operator.
• getInstance Return an instance that is described by its parameters but cannot be said to have the same value. Used with Singletons (later). Used in provider frameworks.