Object-Oriented Design Interview

Object-Oriented Design Interview Questions

Object-oriented design (OOD) interviews ask you to design class hierarchies for real-world systems: parking lot, chess game, elevator system, library management. They test SOLID principles, design patterns, and your ability to model real-world entities in code.

The OOD interview framework: identify core objects → define relationships → assign responsibilities → apply SOLID principles → discuss extensibility. Start with the nouns (objects) and verbs (methods) in the problem description.

SOLID Principles for Interviews

• Single Responsibility — Each class does one thing
• Open/Closed — Open for extension, closed for modification
• Liskov Substitution — Subtypes must be substitutable for base types
• Interface Segregation — Many small interfaces over one large one
• Dependency Inversion — Depend on abstractions, not concretions

Common OOD Questions

• Design a parking lot system
• Design an elevator system
• Design a library management system
• Design a chess game
• Design a vending machine

OOD complements system design and data structures preparation. Practice with AissenceAI.