This website discusses the Gang of Four Patterns in C++ and Java as well as behavioral, creational, and structural design patterns. Design Patterns are a software engineering concept describing recurring solutions to common problems in software design. The authors Erich Gamma, Richard Helm, Ralph Johnson, and John Vlissides are often referred to as the GoF, or Gang of Four. The site explores the capabilities and pitfalls of object-oriented programming and describes several software design patterns. Part of the appeal of design patterns is that they can be used uniformly over many different languages and syntaxes. The basic structure stays the same; only the details change. It is easy to take a pattern implemented in Java and convert it to C++. Historically the Design Patterns

1. have been locked in the heads of the experts or
2. buried deep in the source code.

What is required is a principled means of extracting, documenting, conveying, applying, and preserving this design experience without undue time and effort.

Design Patterns in software engineering represent a structured approach to solving common problems that occur during software development. Here's an elaboration:

1. Concept Origin:Design Patterns were popularized by the "Gang of Four" (GoF) in their book "Design Patterns: Elements of Reusable Object-Oriented Software." They drew inspiration from the architectural patterns described by Christopher Alexander, suggesting that software design could benefit from similar principles of reusable solutions.
2. Purpose:
   • Reusability:By identifying and defining these patterns, developers can reuse successful designs from one project to another, reducing development time and improving reliability.
   • Maintainability:Patterns often promote modular and flexible code, making it easier to maintain and extend software systems.
   • Communication:They serve as a common vocabulary for developers. When someone mentions they're using the "Singleton" or "Factory" pattern, other developers immediately understand the basic structure and intent.
3. Types of Design Patterns:
   • Creational Patterns:Focus on object creation mechanisms, where objects are created in a manner suitable to the situation. Examples include Singleton (ensures a class has only one instance), Factory Method (creates objects without specifying the exact class), and Prototype (creates new objects from an existing object).
   • Structural Patterns:Deal with object composition. These achieve flexibility in an object's structure. Examples include Adapter (allows incompatible interfaces to work together), Decorator (adds responsibilities to objects dynamically), and Composite (treats individual objects and compositions of objects uniformly).
   • Behavioral Patterns:Concerned with communication between objects. They help manage algorithms, relationships, and responsibilities between objects. Examples include Observer (notifies other objects of changes), Strategy (defines a family of algorithms, encapsulates each one, and makes them interchangeable), and Command (encapsulates a request as an object).
4. Benefits:
   • Code Flexibility:Patterns like Strategy or Observer allow for changes in behavior or structure without altering existing code.
   • Efficiency:By using established solutions, developers avoid reinventing the wheel, which can lead to more efficient development cycles.
   • Best Practices:They embody best practices and principles like SOLID (Single Responsibility, Open/Closed, Liskov Substitution, Interface Segregation, Dependency Inversion), promoting cleaner, more maintainable code.
5. Criticism and Considerations:
   • Overuse:There's a risk of over-engineering or using patterns where they're not needed, leading to unnecessary complexity.
   • Learning Curve:For newcomers to programming or specific languages, understanding and implementing design patterns can be challenging.
   • Context Dependency:Not all patterns are universally applicable; they must be chosen based on the specific needs of the project, its scale, and its requirements.
6. Evolution: Over time, new patterns have emerged, especially in areas like enterprise application architecture (e.g., Microservices), web development (e.g., MVC - Model-View-Controller), or even in newer paradigms like functional programming.

Design Patterns, therefore, act as a toolkit for developers, offering tried-and-true solutions that can be adapted to fit various software design challenges, promoting better software architecture, and facilitating easier collaboration among developers by providing a shared language for design solutions.

A pattern must explain why a particular situation causes problems and why the proposed solution is considered a good one. Common design problems arise from "conflicting forces" such as the conflict between breaking the speed of sound and preventing the aircraft from disintegrating. These values, used by the pattern's author to determine which solution is "best", must also be documented within the pattern. A pattern must also explain when it is applicable. Since two houses may be very different from one another, a design pattern for houses must be broad enough to apply to both of them, but not so vague that it doesn't help the designer make decisions. The range of situations in which a pattern can be used is called its context. Some examples might be "all houses", "all two-story houses", or "all places where people spend time". The context must be documented within the pattern.
This website is about design patterns that describes simple and elegant solutions to specific problems in object-oriented software design. Design patterns capture solutions that have developed and evolved overtime and they are not the designs people tend to generate initially. They reflect untold redesign and recoding as developers have struggled for greater reuse and flexibility in their software. The origins of object oriented design is debated, but the first languages that supported OO were Simula and SmallTalk. The site includes code examples in C++ and Java. Design patterns capture these solutions in a succinct and easily applied form.
The design patterns do not require.

1. unusual language features or
2. amazing programming techniques.

All can be implemented in standard object-oriented languages, though they might take a little more effort than ad hoc solutions. Once you understand the design patterns and have had a revelation with them, you will not think about object-oriented design in the same way and will have insights that can make your own designs more flexible, modular and reusable.