Kotlin Interview Questions And answers

1. What is Kotlin?

Ans : Kotlin is a statically-typed programming language developed by JetBrains. It runs on the Java Virtual Machine (JVM) and is interoperable with Java.

2. What are the key features of Kotlin?

Ans : Key features of Kotlin include null safety, concise syntax, type inference, extension functions, coroutines for asynchronous programming, and interoperability with Java.

3. What is the difference between val and var in Kotlin?

Ans :  'val' is used to declare a read-only (immutable) variable, while 'var' is used to declare a mutable variable whose value can be changed.

4. What is the Elvis operator in Kotlin?

Ans : The Elvis operator (?:) is used to provide a default value when a nullable expression evaluates to null. It returns the left-hand side if it's not null, or the right-hand side otherwise.

5. What is a data class in Kotlin?

Ans : A data class is a special type of class in Kotlin that is designed to hold data. It automatically generates useful methods like equals(), hashCode(), toString(), and copy().

6. What are extension functions in Kotlin?

Ans : Extension functions allow you to add new functions to existing classes without modifying their source code. They provide a way to extend the functionality of classes.

7. What is the difference between lateinit and lazy initialization in Kotlin?

Ans : 'lateinit' is used to declare a non-null variable that will be initialized later, whereas 'lazy' is used to declare a lazily initialized variable that is computed only when accessed for the first time.

8. Explain the concept of null safety in Kotlin.

Ans : Null safety in Kotlin helps prevent null pointer exceptions by distinguishing between nullable and non-nullable types. It encourages safe handling of nullable variables and provides operators like ? and !! for null safety.

9. What are sealed classes in Kotlin?

Ans : Sealed classes are used to represent restricted class hierarchies. They can only be subclassed within the same file and are often used in when expressions to cover all possible cases.

10. How are coroutines used in Kotlin?

Ans : Coroutines are used for asynchronous programming in Kotlin. They allow you to write non-blocking code in a sequential and synchronous manner, making asynchronous operations more readable and manageable.

11. What is a companion object in Kotlin?

Ans : A companion object is a singleton object associated with a class. It allows access to its members without needing an instance of the class. It is often used to create static-like methods and properties in Kotlin.

12. How is type inference used in Kotlin?

Ans : Type inference in Kotlin allows the compiler to automatically determine the type of a variable based on its initialization value. This reduces the need for explicit type declarations in many cases.

13. What is the primary constructor in Kotlin?

Ans : The primary constructor in Kotlin is defined in the class header. It is used to initialize the properties of the class. It can include parameter declarations and visibility modifiers.

14. What are higher-order functions in Kotlin?

Ans : Higher-order functions are functions that can accept other functions as parameters or return functions as results. They allow for functional programming paradigms in Kotlin.

15. How does Kotlin support interop with Java?

Ans : Kotlin is fully interoperable with Java, allowing developers to call Java code from Kotlin and vice versa without any issues. Kotlin can use Java libraries, frameworks, and existing code seamlessly.

16. What is the purpose of the 'with' function in Kotlin?

Ans : The 'with' function in Kotlin allows you to perform a series of operations on an object without explicitly referencing the object. It provides a concise way to work with an object's properties and functions.

17. What is a lambda expression in Kotlin?

Ans : A lambda expression is a concise way to define an anonymous function in Kotlin. It allows you to pass functions as arguments or assign them to variables.

18. How do you handle exceptions in Kotlin?

Ans : In Kotlin, exceptions are handled using try-catch blocks. You can catch specific exceptions using multiple catch blocks or use the 'finally' block for code that should always execute, regardless of whether an exception is thrown.

19. How do you iterate over a collection in Kotlin?

Ans : In Kotlin, you can use various approaches to iterate over a collection, including for loops, forEach loops, and higher-order functions like map(), filter(), and reduce().

20. What is the purpose of the 'let' function in Kotlin?

Ans : The 'let' function in Kotlin is used to execute a block of code on a nullable object only if it is not null. It provides a safe way to perform operations on nullable objects without the need for explicit null checks.

21. What are the different types of function parameters in Kotlin?

Ans : Kotlin supports three types of function parameters: positional parameters, named parameters, and default parameters. Named and default parameters provide flexibility when calling functions.

22. Explain the use of the 'in' and 'out' keywords in Kotlin generics.

Ans : The 'in' keyword is used for contravariant type parameters, allowing a type to be used as an input. The 'out' keyword is used for covariant type parameters, allowing a type to be used as an output.

23. What is the purpose of the 'apply' function in Kotlin?

Ans : The 'apply' function is used to configure an object by executing a series of operations on it. It returns the object itself, allowing for a fluid and concise way to set properties and call functions.

24. How do you create a range in Kotlin?

Ans : In Kotlin, you can create a range using the '..' operator. For example, '1..10' represents a range from 1 to 10, inclusive.

25. What are companion properties in Kotlin?

Ans : Companion properties are properties declared inside a companion object. They are similar to companion objects, but they represent static properties associated with a class.