An object that represents the lack of an object.

• null
• design
• pattern

An object responsible for the creation of another object(s)

• abstract
• factory
• design
• pattern

An invariant concrete process that utilizes abstract sub-processes

• template
• design
• pattern

An object that represents a request for another object to do something.

• command
• design
• pattern

Decouples the model from the view in a large system

• MVC
• model
• view
• controller
• design
• pattern

Allows an object to dynamically change its behaviors as per different states of being.

• state
• design
• pattern

Represents a recursive data structure

• composite
• recusive
• recursion
• design
• pattern

Enables the decoupling of a data structure from its algorithms

• visitor
• double-dispatch
• design
• pattern

Allows the reuse of objects in a larger set of objects

• flyweight
• design
• pattern

Allows for decoupled communications between two objects that expect different interfaces.

• adapter
• design
• pattern

Provides an abstract means of performing particular operations for an object.

• strategy
• design
• pattern

Add functionality to an existing module at run-time.

• decorator
• design
• pattern

Enables centralized, transparent, one-way communications to a set of decoupled objects

• observer
• observable
• design
• pattern

Enables only a single instance of a class to exist.

• singleton
• design
• pattern

Recursive algorithms on composite structures

• interpreter
• recursion
• composite
• design
• pattern

Decouples a data structure from its algorithms

• visitor
• data
• structure
• algorithm
• double-dispatch
• design
• pattern