behavioural design patterns

• Command
  Encapsulate a command request as an object
• Interpreter
  A way to include language elements in a program.
• Iterator
  Sequentially access the elements of a collection.The Iterator provides ways to access elements of an aggregate object sequentially without exposing the underlying structure of the objec
• Mediator
  Defines simplified communication between classes.
• Null Object
  Designed to act as a default value of an object
• Observer
  A way of notifying change to a number of classes
• State
  Alter an object's behavior when its state changes
• Strategy
  Encapsulates an algorithm inside a class
• Template method
  Defer the exact steps of an algorithm to a subclass
• Visitor
  Defines a new operation to a class without change

Command;

The Command pattern allows requests to be encapsulated as objects, thereby allowing clients to be parametrized with different requests.