Abstract Factory pattern - Creational

• Factory of factories 
• creates a factory of related objects using abstraction
• provides one level of interface higher than the factory pattern
• used to return one of several factories

Where to use ?

• A system needs independent of how its products are created, composed, and represented
• An alternative to Facade to hide platform-specific classes
• Interface for creating a family of related objects, without explicitly specifying their classes.
• Only the product interfaces are revealed, the implementations remains hidden to the clients

Implementation example

• Interface Color implemented by 3 concrete classes Red, Green & Blue
• Interface Shape implemented by 3 concrete classes Circle, Rectangle & Square
• Abstract class AbstractFactory having 2 methods to get both types of objects (for returning Color and Shape reference types)
• 2 Factory classes (ColorFactory and ShapeFactory) implementing the common abstract class AbstractFactory. Both are returning specific types of objects based on parameter passed
• Class FactoryProvider having method to return specific factory object (return type AbstractFactory) based on passed parameter
• Client will get a factory object (AbstractFactory type) by passing parameter (factory-name) by calling FactoryProvider
• Then Client will get the object by passing parameter to  AbstractFactory

Example of Abstract factories

• java.sql.Connection
  Abstract factory which create Statements, PreparedStatements, CallableStatements,... for each database type.
• java.awt.Toolkit
  Abstract superclass of all actual implementations of the AWT.
  Subclasses of Toolkit are used to bind the various components to particular native toolkit implementations (Java AWT)
• javax.swing.LookAndFeel
  Abstract Swing factory to switch between several look and feel for the components displayed (Java Swing)