Object-Oriented Programming interview questions and quick answers

Yes. It cannot be instantiated directly, but a subclass constructor calls it with super() so the parent's fields get initialised.

An abstract class is a partially built parent that can hold state, constructors and shared code, and a class can extend only one. An interface is a contract of methods that a class promises to provide, and a class can implement many.

Abstraction decides what to show: it exposes a simple view and hides complexity. Encapsulation decides how to protect: it bundles data with methods and restricts access to it.

Constructors are never inherited; a child must define its own and call the parent's with super(). Private members exist inside the child object but cannot be accessed by name from the child.

No. A static method in a child with the same signature hides the parent's one. The call is resolved at compile time from the reference type, so there is no runtime polymorphism.

A class is a blueprint that describes the fields and methods something will have. An object is one real instance built from that blueprint, with its own values stored in memory.

Saying abstract classes cannot have constructors because they cannot be instantiated.

"Yes, abstract classes have constructors, used through super() to initialise shared fields. The class cannot be instantiated on its own, but its constructor runs whenever a concrete subclass object is built."