What are Factory classes and Factory methods in java?

Question

could anybody please explain me what are called Factory Classes and Factory methods in java programming language?

Thanks in advance

Answer 1

When you first learn to develop object in Java, you use the operator called "new", along with a constructor to create an object.

Sometimes, you want to have more control and you can make your constructor private so that it can't be called from outside of your class.  Then for a caller outside of the class, you would develop a factory method that would create an object of that class by calling the constructor from the factory method.

In short, a "factory method" exists to control the way in which the object is created by forcing the caller to create an object using the a call to the factory method instead of by directly calling a constructor.

Answer 2

see it in google

it is concept of middleware

i am not clear in concept

but heared about it

for combining more than one components in J2EE in home serverside

Answer 3

The ideas are more general than Java. These are Design Patterns that can be implemented in any OO language.

Factory is a creational Design Pattern. There is an Abstract Factory, which is a class-level pattern and a Factory Method pattern at the object level.

Often, there are several different classes that provide related services in very different ways. A client only knows that it needs a service and only needs to know the name of the method that provides that service, not what the object implementation of the service is. The Factory pattern allows the service to decide for itself which of the various forms of object should be returned to the client to satisfy the request.

Abstract Factory

UML

http://www.apwebco.com/gofpatterns/creat...

Discussion

http://en.wikipedia.org/wiki/Abstract_fa...

Factory Method

UML

http://www.apwebco.com/gofpatterns/creat...

Discussion

http://en.wikipedia.org/wiki/Factory_met...