Scala Quiz - MCQ Questions and Answers

Welcome to our Scala Quiz! This quiz consists of 25 multiple-choice questions designed to test your understanding of Scala, a powerful and versatile programming language that combines object-oriented and functional programming principles. You'll be challenged on topics ranging from basic syntax and control structures to Scala's sophisticated type system, case classes, and pattern matching. 

Whether you're a newcomer looking to solidify your Scala fundamentals or an experienced programmer aiming to refine your expertise, this quiz thoroughly assesses your skills. Ready to put your Scala knowledge to the test? Let’s get started and see how well you know Scala!

1. What is Scala primarily used for?

a) Web development
b) Mobile development
c) Concurrent and functional programming
d) Embedded systems

2. What does the val keyword signify in Scala?

a) A mutable variable
b) An immutable value
c) A method
d) A class type

3. How do you define a function in Scala that takes one integer parameter and returns its square?

def square(x: Int): Int = x * x
a) By using the def keyword and specifying the return type
b) By using the func keyword and automatically inferring the type
c) By using the function keyword without specifying the type
d) By using the method keyword and inferring the type

4. What is the output of the following Scala code?

val list = List(1, 2, 3)
a) 1
b) 2
c) 3
d) List(1)

5. Which collection in Scala is immutable by default?

a) ArrayBuffer
b) MutableList
c) List
d) Array

6. How do you create a singleton object in Scala?

a) Using the class keyword
b) Using the object keyword
c) Using the singleton keyword
d) Using the one keyword

7. What will the following Scala code output?

val numbers = Set(1, 2, 2, 3)
a) 4
b) 3
c) 2
d) Error

8. Which method can you use to filter elements in a list in Scala?

a) select
b) collect
c) filter
d) map

9. What is pattern matching in Scala?

a) Switching between different patterns of code execution.
b) A way to check for the presence of a pattern in a string.
c) A feature similar to switch-case in other languages, but much more powerful.
d) A method to change the internal structure of an object.

10. How do you declare a variable that can be reassigned in Scala?

var count = 10
count = 15
a) var
b) val
c) def
d) mutable

11. What does the following Scala code return?

def add(a: Int, b: Int) = a + b
add(1, 2)
a) 3
b) 1
c) 2
d) Error

12. How do you handle exceptions in Scala?

a) Using the try and catch blocks
b) Using the try and except blocks
c) Using the fault and catch blocks
d) Using the error and handle blocks

13. What is the use of the yield keyword in Scala?

val numbers = List(1, 2, 3, 4)
val squares = for (n <- numbers) yield n * n
a) It generates a new collection from a for-loop.
b) It pauses the execution of a loop.
c) It exits the loop immediately.
d) It repeats the loop indefinitely.

14. What is an implicit parameter in Scala?

a) A parameter that is passed to a function without being explicitly stated in the function call.
b) A mandatory parameter that must always be specified.
c) A parameter that can only be passed explicitly.
d) A parameter that defaults to null.

15. What will the following Scala code output?

object Main extends App {
    val language = "Scala"
    language match {
        case "Java" => println("Java")
        case "Scala" => println("Scala")
        case _ => println("Unknown")
a) Java
b) Scala
c) Unknown
d) Error

16. How do you concatenate strings in Scala?

val greeting = "Hello, " + "World!"
a) Hello, World!
b) Hello, + World!
c) Compilation error
d) Runtime error

17. How do you define a case class in Scala?

a) Using the case keyword before the class definition.
b) Using the case keyword inside the class definition.
c) By inheriting from a special CaseClass trait.
d) It is not possible to define case classes in Scala.

18. What will the following Scala code output?

def printParam(param: String = "Scala") = println(param)
a) Scala
b) ""
c) null
d) Error

19. What is the purpose of sealed trait in Scala?

a) To prevent the trait from being extended in any file other than where it is defined.
b) To ensure that a trait can only be implemented by a predefined set of classes.
c) To make a trait available across different modules without importing.
d) To encrypt the implementations of a trait.

20. How do you declare a multi-dimensional array in Scala?

val matrix = Array.ofDim[Int](2, 2)
matrix(0)(0) = 1
matrix(0)(1) = 2
matrix(1)(0) = 3
matrix(1)(1) = 4
a) 2x2 Array of Integers
b) 1x4 Array of Integers
c) Compilation error
d) Runtime error

21. What does the flatMap method do in Scala?

a) It merges multiple collections into a single collection after applying a function.
b) It flattens a collection of collections into a single collection.
c) It maps each element to a new collection and then flattens the result.
d) It performs a recursive flat operation on each element.

22. How do you create an anonymous function in Scala?

val sum = (a: Int, b: Int) => a + b
a) By using the => symbol to define the function body.
b) By declaring it with the def keyword.
c) By specifying the function name.
d) It is not possible to create anonymous functions in Scala.

23. What is the default visibility of Scala methods?

a) Public
b) Private
c) Protected
d) Internal

24. What will the following Scala code output?

val nums = List(1, 2, 3)
val doubled = * 2)
a) List(2, 4, 6)
b) List(1, 2, 3)
c) [2, 4, 6]
d) Error

25. How do you handle optional values in Scala?

a) Using the Option class with its subtypes Some and None.
b) Using special if statements.
c) By using the Optional keyword.
d) Scala does not support optional values.