Browse topic-based Kotlin practice sets.
43 practice sets · Page 2 of 3
What is delay() in Kotlin Coroutines?
Suspends the coroutine without blocking the thread
A loop control
Constructs methods dynamically
References constructors
Correct Answer: A — Suspends the coroutine without blocking the thread
Explanation:
The delay() function is a coroutine-friendly way to pause execution without blocking the thread, allowing other coroutines to run.
launch
{
println("Starting coroutine")
delay(1000)
println("Delayed message")
}
What are Coroutines in Kotlin?
Constructor references
Lightweight threads for asynchronous programming
A loop control mechanism
Placeholders for arrays
Correct Answer: B — Lightweight threads for asynchronous programming
Explanation:
Coroutines in Kotlin are a powerful way to handle asynchronous and concurrent programming efficiently. They allow you to perform background tasks without blocking the main thread.
import kotlinx.coroutines.*
fun main() = runBlocking
{
launch
{
println("Running a coroutine")
}
}
What is the purpose of the by keyword in Kotlin?
Type casting
Inheritance
Delegation
Annotation processing
Correct Answer: C — Delegation
Explanation:
The by keyword is used for delegation in Kotlin. For example, with by lazy, initialization of a property is deferred until it is first accessed.
What is the difference between == and === in Kotlin?
Both check for equality
== checks reference equality, and === checks structural equality
== checks structural equality, and === checks reference equality
Both check structural equality
Correct Answer: C — == checks structural equality, and === checks reference equality
Explanation:
In Kotlin, == checks for structural equality (equivalent content), while === checks for reference equality (whether both references point to the same object).
What does the Elvis operator (?:) do in Kotlin?
Performs null checks
Throws exceptions
Converts types
Provides a default value if the left-hand expression is null
Correct Answer: D — Provides a default value if the left-hand expression is null
Explanation:
The Elvis operator (?:) provides a default value when the left-hand expression evaluates to null, e.g., val result = value ?: "Default".
Kotlin uses 1 and 0 to represent Boolean values.
True
False
Correct Answer: B — False
Explanation:
Boolean values are represented using true or false in Kotlin. Kotlin does not represent Boolean as 0/1 or Yes/No or Right/Wrong or Correct/Incorrect etc. So, Correct answer is false.
Which of the following is a correct way to create a list in Kotlin?
val myList = listOf("A", "B", "C")
val myList = mutableList("A", "B", "C")
val myList = ListOf("A", "B", "C")
val myList = createList("A", "B", "C")
Correct Answer: A — val myList = listOf("A", "B", "C")
Explanation:
In Kotlin, the listOf function is used to create an immutable list. For example, val myList = listOf("A", "B", "C") creates a list that cannot be modified.
Which function is used to iterate over a collection in Kotlin?
iterate()
forEach()
loop()
foreach()
Correct Answer: B — forEach()
Explanation:
The forEach() function in Kotlin is used to iterate over a collection or array and execute a block of code for each element.
Which of the following is a correct example of a lambda expression in Kotlin?
fun (x, y) = x + y
(x: Int, y: Int) => x + y
lambda(x, y -> x + y)
{ x, y -> x + y }
Correct Answer: D — { x, y -> x + y }
Explanation:
Lambda expressions in Kotlin are defined using curly braces {}. The syntax includes parameters, followed by ->, and then the body of the lambda, e.g., { x, y -> x + y }.
What is the purpose of the sealed class in Kotlin?
To prevent nullability issues
To define a class with only static members
To create a hierarchy of related classes with restricted inheritance
To create a mutable class
Correct Answer: C — To create a hierarchy of related classes with restricted inheritance
Explanation:
A sealed class in Kotlin restricts inheritance to a defined set of subclasses, making it useful for representing restricted hierarchies and exhaustive when expressions.
Which operator is used in Kotlin for string interpolation?
$
@
%
Correct Answer: A — $
Explanation:
In Kotlin, you use the name" replaces $name with the value of the name variable.
What is a data class in Kotlin used for?
To manage multithreading
To define abstract methods
To hold data without boilerplate code
To store immutable objects only
Correct Answer: C — To hold data without boilerplate code
Explanation:
A data class in Kotlin is designed to hold data. It automatically provides methods like toString(), equals(), hashCode(), and copy(), reducing boilerplate code.
What is the purpose of the fun keyword in Kotlin?
To declare a class
To define a constant
To create a loop
To declare a function
Correct Answer: D — To declare a function
Explanation:
In Kotlin, the fun keyword is used to define a function. For example, fun sayHello() {} is a simple Kotlin function declaration.
Which keyword is used in Kotlin to declare a mutable variable?
let
mutable
var
val
Correct Answer: C — var
Explanation:
In Kotlin, the var keyword is used to create a mutable variable. You can change the value of a var after its initial assignment.
How do you define a single-line function in Kotlin?
Use the inline keyword
Use an equals sign = followed by the expression
Use curly braces {}
Use the return keyword
Correct Answer: B — Use an equals sign = followed by the expression
Explanation:
In Kotlin, single-line functions can be defined concisely using an equals sign = followed by the expression, e.g., fun add(a: Int, b: Int) = a + b.
Which of the following is used to declare an immutable variable in Kotlin?
const
let
var
val
Correct Answer: D — val
Explanation:
In Kotlin, val is used to declare an immutable (read-only) variable.
What does the lateinit keyword in Kotlin indicate?
A variable that is initialized in the constructor
A variable that can never be null
A variable that is private
A variable that is declared but not immediately initialized
Correct Answer: D — A variable that is declared but not immediately initialized
Explanation:
The lateinit keyword in Kotlin is used for variables that are initialized after declaration. It is often used for properties that are initialized in a lifecycle method or dependency injection.
What is a primary constructor in Kotlin?
A special member function
A function that initializes variables
A concise way to initialize a class
A type of class
Correct Answer: C — A concise way to initialize a class
Explanation:
In Kotlin, the primary constructor is a concise way to initialize a class. It is declared in the class header and can include parameters to initialize properties.
Which of the following are primitive data types in Kotlin?
String, Array, Stack, Queue
Boolean, Byte, Short, Int, Float, Long, Double, Char
There are no Primitive data types in Kotlin only Non-Primitive data types
boolean, byte, short, int, float, long, double, char
Correct Answer: B — Boolean, Byte, Short, Int, Float, Long, Double, Char
Explanation:
In Kotlin all primitive data types are Objects. So, they start with Capital Letters. Unlike java, it doesn't use the Wrapper class for primitive data types to behave like Objects. It reduces the confusion of two different Implementation of Numbers type which makes Kotlin more concise.
Which of the following is a primary feature of Kotlin?
Null safety
No semicolons
Lambda expressions
All of the mentioned
Correct Answer: D — All of the mentioned
Explanation:
Kotlin provides many modern programming features, including null safety to prevent NullPointerExceptions, lambda expressions for functional programming, and a concise syntax that omits semicolons.
