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Top Basic Kotlin Interview Questions and Answers for Capgemini

Introduction

Are you preparing for a Kotlin interview at Capgemini? Kotlin is widely used for Android development, backend services, and enterprise applications. Capgemini often asks fundamental Kotlin questions to assess a candidate’s understanding of the language.

In this guide, we have compiled a list of basic Kotlin interview questions that will help freshers and experienced candidates crack their Capgemini technical interview.

✔ Covers key Kotlin fundamentals
✔ Includes real-world examples
✔ Perfect for freshers and experienced professionals

📌 Bookmark this page and review these questions before your Capgemini interview! 🚀

Top Basic Kotlin Interview Questions and Answers

1. What is Kotlin?

Answer: Kotlin is a statically typed, modern programming language developed by JetBrains. It is interoperable with Java, making it ideal for Android development, backend applications, and cross-platform development.

2. What are the key features of Kotlin?

Answer:

• Concise syntax (less boilerplate code than Java)
• Null safety (prevents NullPointerException)
• Interoperability with Java
• Coroutines for asynchronous programming
• Extension functions to enhance existing classes
• Smart casts for type safety

3. What is the difference between var and val?

Answer:

• var – Mutable variable (value can change).
• val – Immutable variable (like final in Java).

Example:

var age = 25  // Can be changed
age = 30  

val name = "Kotlin"  // Cannot be changed
// name = "Java"  // Error

4. What is type inference in Kotlin?

Answer: Type inference means Kotlin automatically determines the type of a variable, so explicit type declaration is not required.

Example:

val message = "Hello, Kotlin!"  // Kotlin infers message as String
val number = 10  // Kotlin infers number as Int

5. How does Kotlin handle null safety?

Answer: Kotlin prevents NullPointerException by making all types non-nullable by default. You must explicitly allow nulls using ?.

Example:

var name: String? = null  // Nullable type
println(name?.length)  // Safe call operator (won't crash)

6. What is the Elvis operator (?:) in Kotlin?

Answer: The Elvis operator (?:) is used to provide a default value if a nullable variable is null.

Example:

val name: String? = null
val length = name?.length ?: 0  // If name is null, return 0
println(length)  // Output: 0

7. What is a when expression in Kotlin?

Answer: when is an advanced replacement for switch statements in Java.

Example:

val number = 2
val result = when (number) {
    1 -> "One"
    2 -> "Two"
    3 -> "Three"
    else -> "Unknown"
}
println(result)  // Output: Two

8. How do you define a function in Kotlin?

Answer: A function in Kotlin is defined using the fun keyword.

Example:

fun greet(name: String): String {
    return "Hello, $name!"
}
println(greet("John"))  // Output: Hello, John!

9. What is a default parameter in Kotlin?

Answer: Kotlin allows default values for function parameters.

Example:

fun greet(name: String = "Guest") {
    println("Hello, $name!")
}

greet()  // Output: Hello, Guest!
greet("John")  // Output: Hello, John!

10. What is the difference between == and === in Kotlin?

Answer:

• == – Compares values (like .equals() in Java).
• === – Compares object references (checks if both variables point to the same object in memory).

Example:

val a = "Kotlin"
val b = "Kotlin"
println(a == b)  // Output: true (compares values)
println(a === b)  // Output: true (points to the same object in memory)

11. How do you declare a class in Kotlin?

Answer:

class Person(val name: String, val age: Int)

Example:

val person = Person("John", 25)
println(person.name)  // Output: John

12. What is a data class in Kotlin?

Answer: A data class is used to store data and automatically generates equals(), hashCode(), and toString().

Example:

data class User(val name: String, val age: Int)

val user = User("Alice", 30)
println(user)  // Output: User(name=Alice, age=30)

13. What are extension functions in Kotlin?

Answer: Extension functions allow you to add new functions to existing classes.

Example:

fun String.addExclamation(): String {
    return this + "!"
}

println("Hello".addExclamation())  // Output: Hello!

14. What is a Singleton in Kotlin?

Answer: A singleton in Kotlin is created using the object keyword.

Example:

object Database {
    val name = "MyDatabase"
    fun connect() = println("Connected to $name")
}

Database.connect()  // Output: Connected to MyDatabase

15. What is the difference between apply, let, run, and with?

Example:

data class Person(var name: String, var age: Int)

val person = Person("Alice", 25).apply {
    age = 30
}
println(person.age)  // Output: 30