Kotlin : Practice Questions and Answers

The is keyword in Kotlin is used to check the type of an object, similar to the instanceof operator in Java.

The import keyword is used in Kotlin to include specific packages or classes, allowing developers to access them without fully qualifying their names.

In Kotlin, functions that do not explicitly return a value have a default return type of Unit, which is similar to void in Java but is a real type in Kotlin.

Kotlin allows creating single abstract method (SAM) interfaces by defining a functional interface, which can have only one abstract method.

Kotlin allows creating single abstract method (SAM) interfaces by defining a functional interface, which can have only one abstract method.

Extension functions in Kotlin let you add new functionality to existing classes without modifying their source code or inheriting from them.

Kotlin distinguishes between mutable (MutableList, MutableSet) and immutable (List, Set) collections, giving developers more control over data mutability.

In Kotlin, throw is a keyword used to explicitly throw an exception. This helps in signaling errors that must be handled.

fun checkAge(age: Int)

{

if (age < 18)

{

throw IllegalArgumentException("Age must be 18 or older.")

}

}

The filter() function in Kotlin returns a new collection containing only the elements that meet the specified condition.

val numbers = listOf(1, 2, 3, 4)

val evenNumbers = numbers.filter { it % 2 == 0 } // [2, 4]

Inheritance enables a subclass to inherit properties and methods from a superclass, reducing redundancy and promoting reusability.

Scope functions (let, apply, run, with, and also) let you execute code within the scope of an object.

The readLine() function reads input from the console in Kotlin.

The println() function prints output to the console.

A companion object in Kotlin acts like a static context, allowing you to define methods and properties that belong to the class itself rather than its instances.

The with function helps access properties and methods of an object without repeating its reference.

val person = Person("Alice", 30)

with(person)

{

println("Name: $name, Age:$age")

}

Kotlin is fully interoperable with Java, meaning you can call Java code from Kotlin and vice versa without major changes.

DSLs help create concise, domain-specific, and more readable code, enhancing productivity and maintainability.

Annotations in Kotlin are metadata that give additional information about code, such as documentation, compiler instructions, or frameworks.

@Target(AnnotationTarget.FUNCTION)

annotation class TestAnnotation(val message: String)

In Kotlin, an interface contains method signatures and properties but does not provide implementation. It defines the contract that implementing classes must fulfill.

The Kotlin Standard Library contains built-in functions and utilities that simplify many common programming tasks, such as string manipulation and collections.

val message = "Hello".toUpperCase() // Converts string to uppercase