Design Patterns in Java

Classic OOP Design Patterns from GoF, implemented in Java.

Design Patterns Implemented

Structural

• Class Adapter — allows classes with incompatible interfaces to work together by wrapping its own interface around that of an already existing class
• Object Adapter
• Facade — provides a simplified interface to a large body of code
• Composite — composes zero-or-more similar objects so that they can be manipulated as one object
• Decorator — dynamically adds/overrides behaviour in an existing method of an object
• Proxy — provides a placeholder for another object to control access, reduce cost, and reduce complexity
• Flyweight — reduces the cost of creating and manipulating a large number of similar objects
• Bridge — decouples an abstraction from its implementation so that the two can vary independently

Creational

• Factory Method — creates objects without specifying the exact class to create
• Abstract Factory — groups object factories that have a common theme
• Prototype — creates objects by cloning an existing object
• Singleton — restricts object creation for a class to only one instance
• Builder — constructs complex objects by separating construction and representation

Behavioral

• Template Method — defines the skeleton of an algorithm as an abstract class, allowing its subclasses to provide concrete behavior
• Strategy — allows one of a family of algorithms to be selected on-the-fly at runtime
• State — allows an object to alter its behavior when its internal state changes
• Command — creates objects which encapsulate actions and parameters
• Observer — is a publish/subscribe pattern which allows a number of observer objects to see an event
• Mediator — allows loose coupling between classes by being the only class that has detailed knowledge of their methods
• Memento — provides the ability to restore an object to its previous state (undo)
• Iterator — accesses the elements of an object sequentially without exposing its underlying representation
• Visitor — separates an algorithm from an object structure by moving the hierarchy of methods into one object
• Chain of Responsability — delegates commands to a chain of processing objects

License

Licensed under MIT.