Virtual Constructor

Define an interface for creating an object, but let subclasses decide which class to instantiate. Factory Method lets a class defer instantiation to subclasses.

Use the Factory Method pattern when

• a class can't anticipate the class of objects it must create
• a class wants its subclasses to specify the objects it creates
• classes delegate responsibility to one of several helper subclasses, and you want to localize the knowledge of which helper subclass is the delegate

• java.util.Calendar
• java.util.ResourceBundle
• java.text.NumberFormat#getInstance()

• Design Patterns: Elements of Reusable Object-Oriented Software