designpattern

A design pattern is a general, reusable solution to a commonly occurring software design problem. It describes a design problem along with a structure and a template for resolving it, including the participants (objects or classes), their responsibilities, and the collaborations that enable the solution. It is not a finished implementation, but a guide that can be adapted to specific languages and contexts.

The concept gained prominence with the 1994 book Design Patterns: Elements of Reusable Object-Oriented Software by Gamma, Helm, Johnson, and Vlissides. Since then, design patterns have become a standard part of software engineering, helping teams communicate complex design ideas efficiently and reuse proven approaches across projects.

Patterns are typically categorized into creational, structural, and behavioral types. Creational patterns address object creation, with examples such as Singleton, Factory Method, Abstract Factory, Builder, and Prototype. Structural patterns deal with object composition and interfaces, including Adapter, Decorator, Facade, Proxy, Composite, Bridge, and Flyweight. Behavioral patterns focus on object interaction and responsibility distribution, such as Observer, Strategy, Command, State, Visitor, Iterator, Mediator, Chain of Responsibility, and Template Method.

Using design patterns involves understanding the problem context, evaluating trade-offs, and adapting the pattern to the specific language and requirements. They can improve code readability, flexibility, and maintainability, but may introduce unnecessary complexity if misapplied or overused. Patterns complement architectural styles and frameworks, serving as a catalog of reusable solutions rather than a one-size-fits-all prescription. See also design patterns in software development and pattern-oriented software development.