Preparing for an OOP interview in 2026? I put together a guide covering 45 questions that actually come up, from the four pillars all the way to SOLID principles and design patterns.
What's inside
- The four pillars explained with real code, not just definitions
- Encapsulation vs Abstraction, the pair almost everyone mixes up
- Method Overloading vs Overriding
- All 5 SOLID principles, each with a violation and a fix
- 8 design patterns interviewers actually ask about (Singleton, Factory, Observer, Strategy, Decorator, Adapter, and more)
- A full parking lot system design walkthrough
- Java, Python, JavaScript, and C# quirks compared side by side
Whether you're prepping for a frontend, backend, or full stack interview, OOP fundamentals show up everywhere. This guide is built to be skimmed fast and used as an actual reference, not just read once and forgotten.
Full guide here: https://devencyclopedia.com/blog/oop-interview-questions
What OOP interview question trips you up the most? Drop it in the comments.
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