Understanding SOLID Principles, UML Relationships, and Common Design Patterns

The article begins with a greeting from a senior architect and a note about a special gift, then introduces the SOLID principles that guide class design: Single Responsibility, Open‑Closed, Liskov Substitution, Dependency Inversion, Interface Segregation, and the principle of least knowledge.

It then explains common UML relationship types used in class diagrams, including Generalization (inheritance), Realization (interface implementation), Association, Aggregation, Composition, and Dependency, describing their visual notation and code representation.

Following the UML overview, the article enumerates twenty‑two classic design patterns—Factory Method, Abstract Factory, Builder, Prototype, Singleton, Adapter, Bridge, Composite, Decorator, Facade, Flyweight, Proxy, Interpreter, Template Method, Chain of Responsibility, Command, Iterator, Mediator, Memento, Observer, State, Strategy, and Visitor—detailing each pattern’s intent, typical applicability, and key characteristics.

Finally, the piece includes promotional calls to join a WeChat group, obtain interview question collections, and access additional open‑source projects, but the core technical content serves as a concise reference for software engineers seeking to improve architecture quality.