Patterns

Introduction

Patterns exist in nature (Dunes, Grand Canyon), art (Modern, Impressionism), science and mathematics (Fractals, Crystals) and Computer Science (Design Patterns).

Christopher Alexander says, Each pattern describes a problem which occurs over and over again in our environment, and then describes the core of the solution to that problem, in such a way that you can use this solution a million times over, without ever doing it the same way twice . Even though Alexander was talking about patterns in buildings and towns, what he says is true about object-oriented design patterns

Designing object-oriented software is hard, and designing reusable object-oriented software is even harder. Experienced object-oriented designers will tell you that a reusable and flexible design is difficult if not impossible to get "right" the first time. Before a design is finished, they usually try to reuse it several times, modifying it each time.

Computer Science Patterns (Design Patterns)

All well-structured systems are full of patterns. A pattern provides a common solution to a common problem in a given context. A mechanism is a design pattern that applies to a society of classes; a framework is typically an architectural pattern that provides an extensible template for applications within a domain.

Patterns are used to specify mechanisms and frameworks that shape the architecture of your system.

Classification

Design Pattern Sub-Design Pattern Fundamental Delegation Functional Interface Proxy Immutal Marker Interface Creational Abstract Factory Anonymous Subroutine Builder Factory Method Lazy initialization Prototype Singleton Structural Adapter Bridge Composite Container Decorator Extensibility Facade Flyweight Proxy Pipes and Filters Private Class

Design Pattern Sub-Design Pattern Behavioral Chain of responsibility Command Event listener Interpreter Iterator Mediator Memento Observer State Strategy Template method Visitor Single-serving visitor Hierarchical visitor Concurrency Action at a distance Active Object Balking pattern Double checked locking Guarded suspension Half-Sync/Half-Async Leaders/followers Monitor Object Read write lock Scheduler Thread pool Thread-Specific Storage Event handling   Architecture

See also

• All App Labs Java Design Patterns Tutorial
• Links Harm Frielink - Pattern
• Wikipedia Patterns

Modeling

• UML

Books

• AntiPatters, by William J. Brown, Raphael C. Malveau, Hays W. McCormick III, Thomas J. Mowbray. An AntiPattern is a literary form that describes a commonly occurring solution to a problem that generates decidedly negative consequences.
• Design Patterns, Elements of Reusable Object Oriented Software by Erich Gamma, Richard Helm, Ralph Johnson, John Vlissides.
• Head First Design Patterns by by Elisabeth Freeman, Eric Freeman, Bert Bates, Kathy Sierra.
• Java Design Patterns - A Tutorial. by James W. Cooper.
• Refactoring: Improving the Design of Existing Code by Martin Fowler, Kent Beck, John Brant, William Opdyke, Don Roberts.