What are design patterns?

Design patterns are typical, proven solutions to common design problems in object-oriented programming. They do not implement ready-made classes or libraries but provide a template that can be adapted to specific tasks.

Patterns are divided into three main categories:

• Creational: Solve object creation problems.
• Structural: Address class and object composition issues.
• Behavioral: Deal with interaction and responsibility distribution among objects.

Examples of popular patterns:

Category	Pattern	Purpose
Creational	Singleton	Ensures only one instance of a class exists.
Creational	Factory Method	Defines an interface for creating objects but allows subclasses to decide which class to instantiate.
Structural	Adapter	Converts the interface of one class into another expected by clients.
Structural	Decorator	Dynamically adds new behaviors to objects.
Behavioral	Observer	Defines a one-to-many dependency between objects so that when one object changes its state, all dependents are notified and updated automatically.
Behavioral	Strategy	Defines a family of algorithms, encapsulates each one, and makes them interchangeable.

Using patterns simplifies code maintenance and extension, improves readability, and promotes best development practices.