Kotlin Kotlin Classes and Object-Oriented Programming 3

Question 1

What is the `by lazy` delegation in Kotlin?

Accepted Answer

Initializes a property only on first access and caches the result

Answer

`by lazy` creates a lazily-initialized property — the initializer lambda runs only the first time the property is accessed, and the result is cached.

Question 2

How do you define a property with a custom getter in Kotlin?

Accepted Answer

Defining a `get()` function inside the property declaration

Answer

Kotlin allows defining a custom getter by writing `get() = ...` immediately after the property declaration.

Question 3

What is the difference between `abstract class` and `interface` in Kotlin?

Accepted Answer

Abstract classes can have constructors and state; interfaces cannot have constructors or mutable state

Answer

Abstract classes can have constructors, state (fields), and initialization logic; interfaces can have abstract and default methods but no constructors or stored mutable state.

Question 4

What does the `inner` keyword enable in Kotlin?

Accepted Answer

Allows the nested class to access members of the outer class

Answer

An `inner` class holds a reference to the outer class instance and can access its members, unlike a regular nested class.

Question 5

What is an enum class in Kotlin?

Accepted Answer

A class representing a fixed set of named constants

Answer

An enum class in Kotlin defines a closed set of named constants, each of which is an instance of the enum class itself.

Kotlin Practice Test

Kotlin Practice Test

Kotlin Kotlin Classes and Object-Oriented Programming 3