OOP Pillars

What they ask

The second half of the intern technical call is a conversation, not code: "explain the four pillars of object-oriented programming, with an example for each in the language you used in the assessment."

Expect the interviewer to push on each one:

• Encapsulation: why private fields plus getters instead of public fields? When is a getter itself a smell?
• Abstraction: interface vs abstract class in Java or C#. When would you choose one over the other?
• Inheritance: overriding vs overloading, what super does, why deep hierarchies hurt, and when composition is the better tool.
• Polymorphism: compile-time vs run-time dispatch, and a concrete case where a base-class reference calls a subclass method.

For a fresh-grad round they also drift into basics from the same family: what a constructor is, static vs instance members, and how a Map or a hash set behaves.

What they look for

• Definitions that come with a real example, not textbook sentences.
• Knowing the trade-offs (composition over inheritance, interface segregation) rather than only the vocabulary.
• Comfort switching between "what" and "why": if you say "polymorphism lets us treat objects uniformly", be ready to show a two-line snippet that does it.