oop-guidelisted

# General Object-Oriented Programming Guidelines ## Stances - Prefer composition over inheritance; program to interfaces, reserving abstract classes for shared implementation. - Keep state private; expose behavior through methods. - SOLID: single responsibility, open/closed, Liskov substitution, interface segregation, dependency inversion. - Apply patterns (Factory, Strategy, Observer) only when they simplify code, never speculatively. ## Design smells Recognizers for common OO-design problems and the principle each violates. - **God Object / Large Class**: one class with many responsibilities and low cohesion; split by responsibility (single responsibility). - **Refused Bequest**: a subclass that ignores or throws on inherited behavior breaks the base-class contract (Liskov substitution); prefer composition over that inheritance. - **Downcasting**: a cast that asks "which subtype is this really?" breaks the abstraction and usually signals a Liskov violation; dispatch through the interface instead. - **Divergent Change**: one class edited for many unrelated reasons; separate the reasons into focused classes (single responsibility). - **Parallel Inheritance Hierarchies**: every new subclass in one tree forces a mirrored subclass in another; collapse or fold the hierarchies. - **Alternative Classes with Different Interfaces**: two classes do the same job with unswappable signatures; unify the interface so callers don't choose sides. - **Temporary Field**: a field populated