What GoF patterns do you know?

GoF (Gang of Four) patterns are classic design patterns described in the book "Design Patterns" by four authors. Main groups and examples of patterns:

• Creational:

  • Singleton — ensures a class has only one instance.
  • Factory Method — creates objects through an interface, allowing subclasses to decide which class to instantiate.
  • Abstract Factory — creates families of related objects.
  • Builder — step-by-step creation of a complex object.
  • Prototype — creating objects through cloning.

• Structural:

  • Adapter — converts the interface of a class into another interface.
  • Composite — composes objects into tree structures.
  • Decorator — adds behavior to an object dynamically.
  • Facade — simplifies the interface of a complex subsystem.
  • Proxy — acts as a substitute for an object, controlling access to it.
  • Bridge — separates an abstraction from its implementation.
  • Flyweight — saves memory by sharing common data.

• Behavioral:

  • Observer — subscribes to events and notifies.
  • Strategy — chooses an algorithm at runtime.
  • Command — encapsulates a request as an object.
  • Iterator — provides sequential access to collection elements.
  • Mediator — centralizes interaction between objects.
  • State — changes object behavior when changing state.
  • Template Method — defines the skeleton of an algorithm.
  • Visitor — separates algorithms from data structures.

These are just the main patterns that are often used in Java and other OOP languages.