Kotlin Kotlin Classes and Object-Oriented Programming

Question 1

What is a data class in Kotlin?

Accepted Answer

A class that automatically generates equals, hashCode, copy, and toString

Answer

Kotlin data classes automatically generate `equals()`, `hashCode()`, `toString()`, `copy()`, and component functions based on constructor properties.

Question 2

What keyword makes a Kotlin class open for inheritance?

Accepted Answer

open

Answer

Kotlin classes are final by default; the `open` keyword must be added explicitly to allow a class to be subclassed.

Question 3

Which Kotlin class type cannot be instantiated and may have abstract members?

Accepted Answer

abstract

Answer

An `abstract` class cannot be instantiated directly and may contain abstract members that subclasses must implement.

Question 4

What is a companion object in Kotlin?

Accepted Answer

A singleton object declared inside a class that holds class-level members

Answer

A companion object is a singleton tied to its enclosing class, used to hold factory methods and constants accessible via the class name.

Question 5

How do you declare a primary constructor in Kotlin?

Accepted Answer

Using parameters directly after the class name

Answer

In Kotlin, the primary constructor is declared directly after the class name using parentheses, with optional `val`/`var` to declare properties.

Kotlin Practice Test