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Kotlin Interview Questions
Detailed answers with code examples. Filter by topic and difficulty.
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50 questions
Beginner
Null Safety
What is null safety in Kotlin?
Beginner
Null Safety
What is the Elvis operator (?:) in Kotlin?
Intermediate
OOP
What is a data class in Kotlin?
Intermediate
OOP
What is a sealed class in Kotlin?
Intermediate
Coroutines
What is the difference between launch and async?
Intermediate
Coroutines
What is a suspend function?
Beginner
Collections
What is the difference between List and MutableList?
Intermediate
Lambdas
What is an extension function?
Beginner
Kotlin Basics
What is the difference between val and var?
Beginner
Kotlin Basics
Why is Kotlin preferred for Android?
Beginner
Control Flow
How is when different from Java switch?
Intermediate
Functions
What is a higher-order function?
Intermediate
OOP
What is the difference between abstract class and interface?
Intermediate
Generics
What are reified type parameters?
Intermediate
Coroutines
What is structured concurrency?
Intermediate
Flow
What is the difference between Flow and StateFlow?
Intermediate
Android
Why use ViewModel with Kotlin coroutines?
Beginner
Collections
What is the difference between map and flatMap?
Beginner
Exceptions
Does Kotlin have checked exceptions?
Intermediate
Scope Functions
When should you use apply vs also?
Beginner
Kotlin Basics
What is type inference in Kotlin?
Beginner
OOP
What is a companion object?
Intermediate
Backend
Why use Kotlin with Ktor or Spring?
Advanced
Multiplatform
What is Kotlin Multiplatform (KMP)?
Advanced
Performance
What is the difference between inline and noinline lambdas?
Beginner
Kotlin Basics
What is the difference between val and var?
Beginner
Kotlin Basics
What is Kotlin primarily used for?
Beginner
Strings
How do string templates work?
Beginner
Control Flow
What is the difference between .. and until?
Beginner
Functions
What is a default argument?
Intermediate
Functions
What is tailrec?
Beginner
Collections
Difference between map and filter?
Beginner
OOP
What is a data class?
Intermediate
OOP
Abstract class vs interface?
Beginner
Null Safety
What does !! do?
Beginner
Lambdas
What does it mean in a lambda?
Intermediate
Scope Functions
What does let do?
Beginner
Exceptions
What is try used for?
Intermediate
Generics
What does reified do?
Intermediate
Coroutines
What is runBlocking?
Intermediate
Coroutines
What is coroutineScope?
Intermediate
Coroutines
Main vs IO dispatcher?
Intermediate
Flow
Cold vs hot Flow?
Intermediate
Flow
StateFlow vs SharedFlow?
Beginner
OOP
What is an enum class?
Beginner
OOP
What is a companion object?
Intermediate
Android
Why data classes on Android?
Intermediate
Android
Why sealed classes for UI state?
Intermediate
Backend
Why coroutines in Ktor/Spring?
Advanced
Multiplatform
What is expect/actual?