Type: Behavioral

Purpose: Define a one-to-many dependency between objects so that when one object changes state, all its dependents are notified.

Type: Behavioral

Purpose: Allow an object to alter its behavior when its internal state changes.

Type: Behavioral

Purpose: Define a family  of algorithms, ecapsulate each one and make them interchageable. Lets the algorithm vary independently from clients that use it.

Type: Behavioral

Purpose: Provide a way to access the elements of an aggregate object sequentially without exposing its underlying representation.

Type: Structural

Purpose: Convert the interface of a class into another interface clients expect. Lets classes work together that couldn't otherwise because of incompatible interfaces.

Type: Creational

Purpose: Provides an interface for creating families of related or dependent objects without specifying their concrete class.

Type: Structural

Purpose: Compose objects into tree structures to represent part-whole hierarchies. Lets clients treat individual objects and compositions of objects uniformly.

Type: Structural

Purpose: Attach additional responsibilities to an object dynamically. Provide a flexible alternative to sub-classing for extending functionality.

Type: Creational

Purpose: Define an interface for creating an object, but let subclasses decide which class to instantiate. Lets a class defer instantiation to subclasses.

Type: Structural

Purpose: Provide a unified interface to a set of interfaces in a subsystem. Defines a high-level interface that makes the subsystem easier to use.

Type: Structural

Purpose: Use sharing to support large numbers of fine grained objects efficiently.

Type: Creational

Purpose: Esure a class only has one instance and provide a global point of access to it.

Type: Structural

Purpose: Instead of using a null reference to convey absence of an object (for instance, a non-existent customer), one uses an object which implements the expected interface, but whose method body is empty. The advantage of this approach over a working default implementation is that a Null Object is very predictable and has no side effects: it does nothing.