Factory pattern - Creational

• Refers to the newly created object through a common interface 
• Client asks Factory class to create object by passing the information it needs
• Creates objects without exposing the instantiation logic to the client

          

Where to use & benefits

• A class wants its subclasses to specify the object. 
• need flexibility in adding new types of objects that must be created by the class
• Hide concrete classes from the client.
• provides hooks for subclasses is more flexible than creating objects directly

Implementation

• Interface Color implemented by 3 concrete classes Red, Green & Blue
• Class ColorFactory having method to create object of Red, Green or Blue based on parameter passed and return into Color type reference variable
• Client will create a ColorFactory object and call its method by passing parameter

Examples of Factories

• Provide an XML parser : 
• javax.xml.parsers.DocumentBuilderFactory or SAXParserFactory

• Allows users to decide which protocol to use
• java.net.URLConnection