Abstract Factory

Definition

A software design pattern, the Abstract Factory Pattern provides a way to encapsulate a group of individual factories that have a common theme. In normal usage, the client software would create a concrete implementation of the abstract factory and then use the generic interfaces to create the concrete objects that are part of the theme. The client does not know (nor care) about which concrete objects it gets from each of these internal factories since it uses only the generic interfaces of their products. This pattern separates the details of implementation of a set of objects from its general usage.

UML Diagram

Picture sourced:[1]

Code Example

public abstract class CPU {

   ...

} // class CPU

The concrete widget classes are simply classes that implement the widget interfaces:

class EmberCPU extends CPU {

   ...

} // class EmberCPU

Below is code for a concrete factory class that creates instances of classes to test ember architecture computers:

class EmberToolkit extends ArchitectureToolkit {

   public CPU createCPU() {
       return new EmberCPU();
   } // createCPU()

   public MMU createMMU() {
       return new EmberMMU();
   } // createMMU()
   ...

} // class EmberFactory

Below is the code for the abstract factory class:

public abstract class ArchitectureToolkit {

   private static final EmberToolkit emberToolkit = new

EmberToolkit();

   private static final EnginolaToolkit

enginolaToolkit

     = new EnginolaToolkit();

...

   /**
    * Returns a concrete factory object that is an

instance of the

    * concrete factory class appropriate for the given

architecture.

    */
   static final ArchitectureToolkit getFactory(int

architecture) {

       switch (architecture) {
         case ENGINOLA:
           &nbs

p; return enginolaToolkit;

         case EMBER:
           &nbs

p; return emberToolkit;

           ...
       } // switch
       String errMsg =

Integer.toString(architecture);

       throw new

IllegalArgumentException(errMsg);

   } // getFactory()

   public abstract CPU createCPU() ;
   public abstract MMU createMMU() ;
   ...

} // AbstractFactory

Client classes typically create concrete widget objects using code that looks something like this: public class Client {

   public void doIt () {
       AbstractFactory af;
       af =

AbstractFactory.getFactory(AbstractFactory.EMBER);

       CPU cpu = af.createCPU();
       ...
   } // doIt

} // class Client

Reference

http://en.wikipedia.org/wiki/Abstract_factory_pattern
http://www.dofactory.com/Patterns/PatternAbstract.aspx