Top Scala Interview Question and Answer and Answers for Spark Developers 2023

Updated:01/01/2023 by Computer Hope
Top 50 Scala Interview and Question

Q.1 What is a vector in Scala?
Ans: A vector is a general-purpose data structure that is immutable. We can use it when we want to hold a huge number of elements and want random access to them. This data structure extends the trait IndexedSeq and the abstract class AbstractSeq.

Q.2 Write a few Frameworks of Scala?
Ans: Some of the Frameworks supported by Scala are as follows:
Akka Framework
Spark Framework
Play Framework
Scalding Framework
Neo4j Framework
Lift Framework
Bowler Framework

Q.3 What is Case Classes?
Ans: Case classes provides a recursive decomposition mechanism via pattern matching, it is a regular classes which export their constructor parameter. The constructor parameters of case classes can be accessed directly and are treated as public value

Q.4 What is a closure in Scala?
Ans: A closure is a function whose return value depends on the value of the variables declared outside the function.

Q.5 What is Monad in Scala?
Ans: Monads is a structure that represents sequential computations, Monad is not a class or a trait; monad is a concept.A monad is an object that wraps another object in Scala, In Monad the output of a calculation at any step is the input to the other calculation which runs as a parent to the current step.

Q.6 What is Null in Scala? What is null in Scala? What is difference between Null and null in Scala?
Ans: Null is a Type (final class) in Scala. Null type is available in “scala” package as “scala.Null”. It has one and only one instance that is null.

Q.7 What is ofDim() ?
Ans: In Scala, ofDim() is a function that allows you to create multidimensional arrays. You can store the data in multiple dimensions – it becomes like a matrix of sorts.

Q.8 What is the difference between val and var in Scala?
Ans: In Scala, both val and var are used to define variables. However, they have some significant differences.
var stands for variable.
val stands for value.
As we know, variable means changeable and value means constant.
var is used to define Mutable variables that means we can reassign values once its created.
val is used to define Immutable variables that means we cannot reassign values once its created.
In simple Java terminology, var means ‘variable’ and val means ‘final variable’

Q.9 How can we append to the list
Ans: In Scala, we can ':+' single value. Check out the below given example to understand better.
var myList = List.empty[String]

Q.10 What is an Object in Scala?
Ans: An object in Scala is one particular instance in a class.

Q.11 What is Recursion in Scala?
Ans: Recursion is referred to as the function in Scala that calls itself.

Q.12 What are the different scopes for variables in Scala
Ans: There are three different scopes for variables in Scala, which include Fields, Method Parameters, and Local Variables.

Q.13 What are the features of Yield in Scala?
Ans: feature as follow :
    It is used as a Loop.
  • It produced value for each iteration.
  • It supports the use of Map, FlatMap, and Filters along with nomads.

Q.14 Define Map in Scala?
Ans: A Map in Scala is the collection of key or value pairs that helps in retrieving a Value-Based on its key.

Q.15 Which all languages Apache Spark supports?
Ans: Apache Spark is written in Scala. Many people use Scala for the purpose of development. But it also has API in Java, Python, and R.

Q.16 Why do we need App in Scala?

App is a helper class that holds the main method and its Members together. The App trait can be used to quickly turn Objects into Executable programs. We can have our classes extend App to render the executable code.

object Edureka extends App{
println('Hello World')

Q.17Explain the Scala Anonymous Function?
Ans: In the Source code, Anonymous functions are called ‘Function literals’ and at run time, function literals are instantiated into objects called Function values. Scala provides a relatively easy Syntax for defining Anonymous functions.

(z:Int, y:Int)=> z*y

Q.18 Explain the Syntax for function declaration in Scala?
The syntax is:

def functionName(parameters : typeofparameters) : returntypeoffunction = {
// function statements
A function is created using the ‘def’ keyword.
All the parameters and their return types are mentioned clearly.
The equal operator, when added, returns the value, else if no equal
operator is used, the function will not return any value.

Q.19 How to create Arrays in Scala?
Ans: Array we can declare a variable that reference the array .

we need to describe data type of array .

An array created as :

var z:Array[String] = new Array[String](10)
var z = new Array[Int](5)

Q.20 Explain set collection in scala.
A Set is a collection that contains no duplicate elements. There are two kinds of Sets,

the immutable and the mutable.

By default, Scala uses the immutable Set.

for details

Below is method is use by set

head: returns the head (first element) of the set
tail: returns entire set except the head element
isEmpty: checks if the set is empty, returns Boolean
Example :

scala> val fruit = Set('apple', 'orange', 'peach', 'banana')
fruit: scala.collection.immutable.Set[java.lang.String] = Set(apple, orange, peach, banana)
scala> fruit('peach')
res0: Boolean = true
scala> fruit('potato')
res1: Boolean = false

Q21. Explain implicit classes with syntax.
Implicit classes allow Implicit conversations with the class’s Primary constructor when the class is in scope. Implicit class is a class marked with the “implicit” keyword. This feature was introduced in with Scala 2.10 version.

object {
implicit class Data type) {
def Unit = xyz

List of Scala Interview Question

  1. What is the difference between flatMap() and map() operations?
  2. Write a lambda function in Scala, using map operation, which takes a sequence of salaries as input and outputs double of every element from input.
  3. How will you determine whether a function causes a shuffle or not without the help of documentation?
  4. What is the difference between Singleton and Companion objects?
  5. What happens when we create an instance of a class without the ‘new’ keyword?
  6. What are the types of program evaluation in Scala?
  7. What do you mean by Literals? What are the different types of Scala literals?
  8. What is the difference between var, val and def in Scala?
  9. Can a companion object in Scala access the private members of its companion class in Scala?
  10. Differentiate Scala’s == And Java’s == Operator?
  11. What is pattern matching?
  12. What is for-comprehension in Scala?
  13. What is Seq in Scala collection?
  14. What is a ‘Scala set’? How will you declare immutable set?
  15. How does yield work in Scala?
  16. What is an anonymous object in Scala?
  17. What is ‘Option’ and why it is used in Scala?
  18. How apply and unapply methods used in Scala?
  19. What Is The difference between call-by-value and call-by-name function parameters?
  20. What is the use of Scala's App?
  21. What is the Diamond Problem and how Scala solves it?
  22. What is Monad in Scala?
  23. What is Currying in Scala? What are its advantages?
  24. How many types of constructors are used in Scala?
  25. When using Scala stream, what are the considerations you must undertake?
  26. What Is The Main Reason behind not having “static” keyword like Java in Scala?
  27. What is a higher order function in Scala? Give example.
  28. What is Scala Trait?
  29. What is the difference between Seq and List in Scala?
  30. What is a tail-recursive function in Scala?