Kotlin Questions and Answers for Viva

Answer-1: Kotlin is a modern, statically-typed programming language developed by JetBrains, used for JVM, Android, and more.

Answer-2: Key features include null safety, concise syntax, interoperability with Java, coroutines, and extension functions.

Answer-3: Kotlin offers null safety, concise syntax, extension functions, and default parameter values, unlike Java.

Answer-4: val declares a read-only variable whose value cannot be reassigned.

Answer-5: var declares a mutable variable whose value can be reassigned.

Answer-6: Nullable types are declared with ? (e.g., String?) and allow the variable to hold null.

Answer-7: The Elvis operator returns a default value if the left-hand side is null. Example: a ?: "default".

Answer-8: A data class is a class that automatically generates methods like toString, equals, and hashCode.

Answer-9: Extension functions add functionality to existing classes without modifying them.

Answer-10: Kotlin provides null safety using nullable types (String?) and operators like ?., !!, and ?:.

Answer-11: A sealed class restricts the hierarchy to a predefined set of subclasses, improving type safety.

Answer-12: Coroutines simplify asynchronous programming by providing a lightweight way to handle concurrency.

Answer-13: Use the fun keyword. Example: fun functionName(): ReturnType { }.

Answer-14: Higher-order functions take functions as parameters or return functions.

Answer-15: lateinit is used for variables initialized after declaration, but only for non-nullable types.

Answer-16: lazy initializes variables on first access, while lateinit is for non-nullable vars initialized later.

Answer-17: A companion object holds static members for a class.

Answer-18: == checks structural equality; === checks referential equality.

Answer-19: apply is a scope function that executes a block of code on an object and returns the object.

Answer-20: let returns the lambda result; also returns the original object after applying the lambda.

Answer-21: map transforms elements; flatMap transforms and flattens nested collections.

Answer-22: Inline functions allow their code to be directly inlined at the call site, reducing overhead.

Answer-23: Modifiers include public, private, protected, and internal.

Answer-24: An abstract class cannot be instantiated and can have abstract and non-abstract members.

Answer-25: An interface defines abstract methods and properties and can include default implementations.

Answer-26: Default arguments provide default values to function parameters, making them optional in calls.

Answer-27: Kotlin can call Java code seamlessly and vice versa, due to shared bytecode and annotations.

Answer-28: run executes a block and returns the result; with operates on a receiver and returns the lambda result.

Answer-29: object creates a singleton instance or declares anonymous objects.

Answer-30: Type aliases define alternative names for existing types to improve code readability.

Answer-31: Kotlin collections include List, Set, and Map, with mutable and immutable versions.

Answer-32: A when expression replaces switch statements for branching logic and can return a value.

Answer-33: Unit is a return type for functions that do not return a value, similar to void in Java.

Answer-34: A suspend function is used in coroutines and can pause and resume execution without blocking threads.

Answer-35: Kotlin uses try, catch, and finally blocks to handle exceptions, similar to Java.

Answer-36: A lambda expression is an anonymous function with syntax: { parameters -> body }.

Answer-37: The by keyword delegates property or interface implementation to another object.

Answer-38: Generics enable type-safe operations and reusable code for multiple types.

Answer-39: The is keyword checks if an object is of a specific type at runtime.

Answer-40: Scope functions include let, run, apply, also, and with for concise code within object contexts.

Answer-41: Nothing represents a function that never returns, often used for error signaling.

Answer-42: A backing property is used to customize getters and setters for a property with a private field.

Answer-43: inline avoids lambda overhead by inlining the function's code at the call site.

Answer-44: Smart casts automatically cast variables after type checks with is or !is.

Answer-45: filter selects elements based on a condition; map transforms each element in a collection.

Answer-46: Kotlin provides immutable collections (listOf, mapOf) and val variables for immutability.

Answer-47: tailrec optimizes recursive functions into iterative loops to prevent stack overflow.

Answer-48: @JvmStatic marks methods as static in the Java bytecode, enabling easier interop with Java.

Answer-49: lazy initializes properties lazily on first access, ensuring initialization occurs only once.

Answer-50: Array has a fixed size; List is a more flexible collection with mutable and immutable options.