| Creational Patterns | |
|---|---|
| Name | Description |
| *Factory | Provide an interface for creating families of related or dependent objects without specifying their concrete classes. |
| *Singleton | Ensure a class has only one instance, and provide a global point of access to it. |
| Builder | Separate the construction of a complex object from its representation, allowing the same construction process to create various representations. |
| Lazy Initialization | Tactic of delaying the creation of an object, the calculation of a value, or some other expensive process until the first time it is needed. |
| Structural Patterns | |
|---|---|
| Name | Description |
| Decorator | Attach additional responsibilities to an object dynamically keeping the same interface. Decorators provide a flexible alternative to subclassing for extending functionality. |
| Adaptor | Convert the interface of a class into another interface clients expect.
An adapter lets classes work together that could not otherwise because of incompatible interfaces. |
| Bridge | Decouple an abstraction from its implementation allowing the two to
vary independently. |
| Composite | Compose objects into tree structures to represent part-whole hierarchies. Lets clients treat individual objects and compositions of objects uniformly. |
| Facade | Provide a unified interface to a set of interfaces in a subsystem. Defines a higher-level interface that makes the subsystem easier to use. |
| Flyweight | Use sharing to support large numbers of similar objects efficiently. |
| Proxy | Provide a surrogate or placeholder for another object to control access to it. |
| Behavior Patterns | |
|---|---|
| Name | Description |
| *Iterator | Provide a way to access the elements of an aggregate object sequentially without exposing its underlying representation. |
| *Observer | Define a one-to-many dependency between objects where a state change in one object results in all its dependents being notified automatically. The dependents can then contact the parent, if necessary, to obtain more information. |
| *State | Allow an object to alter its behavior when its internal state changes. The object will appear to change its class. |
| *Strategy | Define a family of algorithms, encapsulate each one, and make them interchangeable. Allows the algorithm to vary independently from the clients that use it. |
| Blackboard | Generalized observer, which allows multiple readers and writers. Communicates information system-wide. |
| Chain of Responsibility | Avoid coupling the sender of a request to its receiver by giving more than one object a chance to handle the request. Chain the receiving objects and pass the request along the chain until an object handles it. |
| Command | Encapsulate a request as an object, thereby letting you parameterize clients with different requests, queue or log requests, and support undo operations. |
| Mediator | Define an object that encapsulates how a set of objects interact. Promotes loose coupling by keeping objects from referring to each other explicitly, and it lets you vary their interaction independently. |
| Memento | Without violating encapsulation, capture and externalize an object's internal state allowing the object to be restored to this state later. Can be used to assist with undo operations. |
| Template | Define the skeleton of an algorithm in an operation, deferring some steps to subclasses. Allows subclasses to redefine certain steps of an algorithm without changing the algorithm's structure. |
| Visitor | Represent an operation to be performed on the elements of an object. Visitor lets you define a new operation without changing the classes of the elements on which it operates. |