Java Design Patterns

by Jeff Hunter, Sr. Database Administrator

Common Java Design Patterns

Pattern Name	Meaning	Examples in Java API
Factory	One class that makes up instances for you, controlled by subclasses	getInstance(in Calendar, Format, Local...); socket constructor; RMI InitialContext
Iterator	Loop over all elements in a collection (or container), visiting each element only once.	Iterator; (or Enumeration for pre Java 2)
Singleton	Only one instance may exist for a given class.	java.awt.Toolkit
Memento	Capture and externalize an object's state for later reconstruction.	Serializing an object
Command	Encapsulate requests, allowing queues of requests, undoable operations, etc.	java.awt.Command
Model-View-Controller	Model represents data; View is what user user sees; Controller responds to user request.	Observer/Observable;