Browse topic-based Kotlin practice sets.
43 practice sets · Page 1 of 3
What is the purpose of the is keyword in Kotlin?
To check the type of an object
To define an interface
To declare a variable
To create a loop
Correct Answer: A — To check the type of an object
Explanation:
The is keyword in Kotlin is used to check the type of an object, similar to the instanceof operator in Java.
Which Kotlin keyword is used to import packages or classes?
package
use
include
import
Correct Answer: D — import
Explanation:
The import keyword is used in Kotlin to include specific packages or classes, allowing developers to access them without fully qualifying their names.
What is the default return type of a Kotlin function that does not return anything?
Nothing
Unit
null
void
Correct Answer: B — Unit
Explanation:
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.
How can you create a single abstract method (SAM) interface in Kotlin?
By using the SAM keyword
By extending an abstract class
By defining a functional interface
By using the object keyword
Correct Answer: C — By defining a functional interface
Explanation:
Kotlin allows creating single abstract method (SAM) interfaces by defining a functional interface, which can have only one abstract method.
What is the default visibility modifier for classes and functions in Kotlin?
private
internal
public
protected Answer: c Explanation: By default, classes and functions in Kotlin are public, meaning they are accessible from anywhere in the project.
Correct Answer: C — public
Explanation:
Kotlin allows creating single abstract method (SAM) interfaces by defining a functional interface, which can have only one abstract method.
Which of the following is true about extension functions in Kotlin?
They override existing class methods
They are only available for Java classes
They require modifying the source code of the class
They allow adding new functionality to existing classes without inheritance
Correct Answer: D — They allow adding new functionality to existing classes without inheritance
Explanation:
Extension functions in Kotlin let you add new functionality to existing classes without modifying their source code or inheriting from them.
What is a key characteristic of Kotlin collections?
Collections automatically resize when accessed
Kotlin separates mutable and immutable collections
Collections are thread-safe by default
All collections are mutable by default
Correct Answer: B — Kotlin separates mutable and immutable collections
Explanation:
Kotlin distinguishes between mutable (MutableList, MutableSet) and immutable (List, Set) collections, giving developers more control over data mutability.
What is throw in Kotlin?
A loop control statement
A constructor reference
Used to explicitly throw an exception
A placeholder array
Correct Answer: C — Used to explicitly throw an exception
Explanation:
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.")
}
}
What is the filter() function in Kotlin?
Selects elements that meet a given condition
Adds numbers together
Manages memory
Replaces elements with strings
Correct Answer: A — Selects elements that meet a given condition
Explanation:
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]
What is inheritance in Kotlin OOP?
A method to repeat operations
A constructor reference
A way to reuse properties and behaviors across multiple classes
A data storage operation
Correct Answer: C — A way to reuse properties and behaviors across multiple classes
Explanation:
Inheritance enables a subclass to inherit properties and methods from a superclass, reducing redundancy and promoting reusability.
What is the scope function in Kotlin?
Functions that let you control variable scope
Used only for inheritance
A loop control structure
Functions like let, apply, run, with, and also
Correct Answer: D — Functions like let, apply, run, with, and also
Explanation:
Scope functions (let, apply, run, with, and also) let you execute code within the scope of an object.
Which method is used to get user input in Kotlin?
readLine()
getInput()
readInput()
scanInput()
Correct Answer: A — readLine()
Explanation:
The readLine() function reads input from the console in Kotlin.
How do you print a message to the console in Kotlin?
console()
print()
println()
echo()
Correct Answer: C — println()
Explanation:
The println() function prints output to the console.
What is the primary purpose of the companion object in Kotlin?
To create multiple instances of a class
To manage threading
To override a class's behavior
To provide a static-like context within a class
Correct Answer: D — To provide a static-like context within a class
Explanation:
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.
What is the with scope function used for in Kotlin?
Constructs dynamic arrays
Handles loops
Simplifies accessing properties and methods of an object
Performs arithmetic operations
Correct Answer: C — Simplifies accessing properties and methods of an object
Explanation:
The with function helps access properties and methods of an object without repeating its reference.
val person = Person("Alice", 30)
with(person)
{
println("Name: age")
}
What does Kotlin interoperability with Java mean?
Only Java constructors are supported
Kotlin replaces all Java features automatically
Kotlin code cannot work with Java
Kotlin seamlessly integrates with Java code in the same project
Correct Answer: D — Kotlin seamlessly integrates with Java code in the same project
Explanation:
Kotlin is fully interoperable with Java, meaning you can call Java code from Kotlin and vice versa without major changes.
What are the key advantages of using a DSL in Kotlin?
Cleaner, more readable code specific to a domain
Faster compilation
Simplifying garbage collection
Memory optimization
Correct Answer: A — Cleaner, more readable code specific to a domain
Explanation:
DSLs help create concise, domain-specific, and more readable code, enhancing productivity and maintainability.
What are Annotations in Kotlin?
Functions that perform looping operations
A form of constructors
Metadata that provides additional information about code
Syntax for string manipulation
Correct Answer: C — Metadata that provides additional information about code
Explanation:
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)
What is an Interface in Kotlin?
A group of functions without any implementation
A constructor reference
A class that contains properties and methods
A loop control mechanism
Correct Answer: A — A group of functions without any implementation
Explanation:
In Kotlin, an interface contains method signatures and properties but does not provide implementation. It defines the contract that implementing classes must fulfill.
What is the Kotlin Standard Library?
A database connector
A constructor placeholder
A collection of Kotlin-specific websites
A set of pre-defined functions and utilities included in the Kotlin core
Correct Answer: D — A set of pre-defined functions and utilities included in the Kotlin core
Explanation:
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
