50 Best Scala Interview Questions And Answers in 2024

Scala Interviews are among the interviews which the students fear. However, there is nothing of that sort, and the worries are just framed by in-confident students. It is therefore advised to stay away from such students or applicants who create rumors or demotivate you. Be sure that the Scala Interviews are meant to select one of the best candidates out of all the applicants who know answers and showcase confidence in replying. Therefore a selection process will continue even if you are in or not in.

So it's better to ascertain your position as a selected candidate in the Scala interview by preparing yourself with academic learning, prompt replying skills, and confident smiling face, which wins faith of the hiring manager as if you are the best candidate for the job.

After researching with the interviewees who faced Scala interview questions, it was observed that the majority were asked similar kinds of questions. We have gathered the 50 best Scala interview questions and answers that could help you better understand what could be asked in the interview process. Also, it has been observed that the confident students were among the successful candidates who passed the Scala Interview tests. These students were not only ready with their academic part but also brought along their faith in themselves ownself, which helped them face all the questions with a smile.

As a result, the interviewees who answered the Scala questions with confidence were able to leave a good impression on the hiring manager and successfully got selected for the job.

Best Scala Interview Questions and Answers

The following are the 50 Best Scala Interview Questions and answers.

Question: Define Scala?

Answer: Scala is a Java-based Hybrid programming language. It combines the features of functional-oriented and object-oriented programming language. It is used by integration with the Java Virtual machine and can compile the written code.

Question:  How is Scala a programming language with a combination of both functional and object-oriented programming?

Answer: Scala programming language treats every single value as an object, which also includes Functions. This way, it is a combination of both functional and object-oriented programming.

Question:  What are the frameworks supported by Scala?

Answer: There are various frameworks supported by Scala that include the following.

1. Spark Framework
2. Play  Framework
3. Akka Framework
4. Neo4j Framework
5. Bowler Framework
6. Scalding Framework
7. Lift Framework

Question: What are the different kinds of variables in Scala?

Answer: There are mainly two types of variables in Scala, which include Mutable variables and Immutable Variables.

Question: Define the features of Mutable Variables?

Answer: The Mutable variables can be declared by using the var keyword. The values in these variables support changes.

Question:  Define the features of Immutable Variables?

Answer: The Immutable Variables can be declared by using the val keyword. The values in these variables do not support changes.

Question:  Define Stream in Scala?

Answer: A stream is defined as a Lazy list, which helps in the evaluation of the elements only when they are needed.

Question: What is the benefit of Streams in Scala?

Answer: The benefit of Streams in Scala is that it helps in enhancing the performance of the program.

Question: What are the advantages of Scala?

Answer: There are several advantages of Scala, which include the following.

1. Scalable
2. Maintainable
3. Productive
4. Concurrent programming
5. Consists of Native Tuples codes Consists of Testable codes
6. Concise code
7. No Boilerplate code
8. Singleton objects are clearer in the solution than static

Question: What are the different operators in Scala?

Answer: The different operators in Scala include the following.

1. Assignment operators
2. Relational operators
3. Logical operators
4. Arithmetic operators
5. Bitwise operators

Question: What is Recursion in Scala?

Answer: Recursion is referred to as the function in Scala that calls itself.

Question: Give an example of Recursion in Scala?

Answer: When  Function A calls function B, which further calls function C, then it is called recursion in Scala and is mostly used in Functional Programming.

Question: What is Tail Recursive?

Answer: Tail recursive is a call back to the function that should be the end task function that is to be performed.

Question: What are Tuples in Scala?

Answer: Tuples in Scala combine the finite numbers of items all together so that the programmer can Pass tuple around as a whole.

Question: How do I Append data in a list?

Answer: To append data in a list, you should use “:+”. This appends a single value to the list. For example:

var a = List.empty[String]
a: List[String] = List()
a:+="pear"

If you want to add a list to another, then use “++” as follows:

a++ = List("mango","banana")

Question: Explain the Syntax for function declaration in Scala?

Answer: The syntax is:

def functionName(parameters : typeofparameters) : returntypeoffunction = {  
// function statements  
} 

Note that the keyword return is not used. Scala determines the return type by seeing the last parameter. 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. 

Question: How to create Arrays in Scala?

Answer: To create an array, we have to declare a variable that references the array and specify the type of array. An array can be created as:

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

Question: Describe Exception Handling in Scala?

Answer: Exception handling in Scala is similar to Java except that there are no checked exceptions. To throw exceptions, we use throw new <ExceptionName> and to catch we can use try{}catch{}blocks. There is also a finally block which is executed at the end. We can catch multiple exceptions inside the catch block using case ex: blocks. Example:

try {
         val input = new FileReader("myinput.txt")
      } catch {
         case ex: FileNotFoundException => {
            println("File not found")
         }
         case ex: IOException => {
            println("Exception in I/O")
         }
      } finally {
         println("Exiting the code...")
      }
    }

Question: What is a ‘Scala set’? What are methods through which operation can be performed on sets?

Answer: Set is a collection that has unique elements (no duplicates). There are two types of sets: mutable and immutable (its value cannot be changed). By default, Scala uses immutable sets. Few methods for set operations are:

• 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

Question: Explain the ways Scala is better than other programming languages?

Answer: A few reasons are:

• Though it is object-oriented, Scala has features of a functional programming language as well.
• It is concise, easy to code, readable, easy to compile and error-free.
• Deploys concurrency thus making synchronization easy.
• Third-party libraries can be added easily in the form of language constructs.
• Works in a multicore architecture environment.

Question: Explain the difference between var and value?

Answer: Both var and value are used for declaring variables. However, var represents a variable whose value can be updated later in the code, whereas val (value) is like a constant or final value which cannot be changed. Once a var or val is assigned a value, its type cannot be changed. Example:

var var1 = new A(6);
var1 = new A(7);
val value = 6;
value = 7; // This will not work

Question: Mention the different types of Scala literals?

Answer: There are many literals in Scala:

• Integer literals: Int or Long, example, 12, 0999L
• Floating-point literal: Float, example, 1.3
• Boolean literals: true/false
• Symbol literals: interned strings, example ‘WHO
• Character literals: single character, example: ‘v’, ‘\t’
• String literals: sequence of characters, for example, “Hi, how are you?”

Question: What is exception propagation in Scala?

Answer: An exception can be thrown in Scala using the . clause and propagated to the next class. It is the same as other programming languages like Java. Example:

 try{
  var fr = new FileReader(“data.txt”)
 }catch {
  case ex: FileNotFoundException =>{
            println("file not found")
  }
  case ex: IOException => {
            println("IO Exception")
         }
}

Question: What is a BitSet?

Answer: BitSet is a collection of smaller integers represented as bits of the larger integer. We can add multiple items in a bitset using the ‘++’ operator similar to list. Bitsets can be mutable and immutable and are sets of non-negative integers.

Question: Is Tuple immutable?

Answer: Yes, Tuple is immutable mostly in the case of Array or List wherein it can hold objects with different datatypes.

Question: What is Class in Scala?

Answer: Class in Scala combines the data and its methods in Scala.

Question: What is an Object in Scala?

Answer: An object in Scala is one particular instance in a class.

Question: Do we need App in Scala?

Answer: Yes, we do need App in Scala so that it could act as a helper class that holds the main method and its members together. 

Question: What is the benefit of App trait? Give an example?

Answer: An App trait can be used for quickly turning the objects into executable programs. For example, we can have our classes extend App with the purpose of rendering the executable code.

Question: Define Higher-order functions?

Answer: Higher-order functions are defined as a function that does one or more of the functions as arguments, returns a function as its result.

Question: What are the different scopes for variables in Scala?

Answer: There are three different scopes for variables in Scala, which include Fields, Method Parameters, and Local Variables.

Question: What are Fields in Scala?

Answer: Fields are variables that are declared inside an object. They can be accessed from any point inside the program, depending upon the access modifiers. It can be declared using val or var.

Question: What are the method parameters?

Answer: Method parameters are Pass values to the methods. They are strictly immutable and can be accessed from inside a method. However, the use of Reference can be made for accessing them from outside the method provided.

Question: What are the local variables?

Answer: Local variables can be accessed if we return them from the method. They are declared inside a method and accessible from there only.

Question: What is a closure in Scala?

Answer: The closure is a function in Scala whose return value is dependent on the value of one or more variables that are declared outside the closure.

Question: Define Traits in Scala?

Answer: Traits in Scala is a unit that encapsulates the method and its variables or field.

Question: What is the difference between Scala and Java?

Answer: The difference between Scala and Java include the following.

Question: What is an extend keyword in Scala?

Answer: An extend keyword in Scala helps in extending a base Scala class so that you can design an inherited class just like it is done in Java by use of extending keywords. 

Question: What are the restrictions in extend key keywords in Scala?

Answer: In Scala, there are two restrictions to extend keywords. This includes the first one as method overriding, which requires override keywords and the second one as a primary constructor that can pass parameters to the base constructor.

Question: Define Implicit classes with syntax in Scala?

Answer: Implicit classes with syntax in Scala supports the implicit conversation with the class’s primary constructor when the class is in scope. It is marked with the “implicit” keyword and introduced in Scala 2.10 version.

Question: What are the different types of Access Modifiers available in Scala?

Answer: Answer: There are three types of Access Modifiers available in Scala, which include Private, Public, and Protected.

Question: What is a Private Access Modifier?

Answer: A Private Access Modifier supports the restriction of the accessibility of a private member to the class or object as a set or declared in advance.

Question: What is Public Access Modifier?

Answer: Public Access Modifier does not require any explicit modifier to allow the public members to get access, and the members can access from anywhere.

Question: What is Protected Access Modifier?

Answer: A Protected Access Modifier supports accessibility only from the subclass of the class where the member is defined and authorized.

Question: Define Monad in Scala?

Answer: Monad in Scala is an object. It helps in wrapping another object as per the mini-program, which can be a function to perform data manipulation, particularly on the underlying object. It indirectly manipulates the object and chooses the method to apply for the program on the underlying object.

Question: What is Scala Anonymous Function?

Answer: Scala Anonymous Function is also known as Function Literals’ in the Source Code. During the run time, these function literals are instantiated into objects, which are known as Function values, which provides a relatively easy Syntax for defining these Anonymous functions.

Question: Why is Immutability preferred in Scala?

Answer: Immutability is preferred in Scala because it supports the design and uses it as a default. It helps in dealing with the Concurrent programs as well as Equality issues.

Question: Define different packages in Scala?

Answer: There are three different packages in Scala. These are,

1. Java.lang._: It is a package that provides classes that are fundamental for the design of the Java programming language.
2. Java.io._: It is a package that imports every class in Scala for input-output resources.
3. PreDef: It offers type aliases for types that are used regularly used in Scala. These include Safe, Map, and the List constructors.

Question: What is the role of Options in Scala?

Answer: Options have a vital role in Scala, which is to Wrap the Missing value.

Question: Define types of Scala Identifiers?

Answer: There are four types of Scala Identifiers, which include,

1. Literal identifiers
2. Alphanumeric identifiers
3. Mixed identifiers
4. Operator identifiers

Question: What are the procedures to compile Scala code?

Answer: The procedure to compile Scala Code starts with the writing of the Code in Scala IDE or Scala REPL, which is later converted into the Byte Code and thereby transferred to Java Virtual Machine or JVM for compilation purpose.

Question: What are the features of Yield in Scala?

Answer: Yield has several features as,

1. It is used as a Loop.
2. It produced value for each iteration.
3. It supports the use of Map, FlatMap, and Filters along with nomads.

Question: Define Null, Nill, None, and Nothing in Scala?

Answer: Null, Nill, None, and Nothing in Scala can be defined as follows.

1. Null denotes the absence of a value.
2. Nil represents the end of a List.
3. None is the value of an option that has no value.
4. Nothing is the lowest type in the type system.

Question: What are the different Loops in Scala?

Answer: There are three different types of Loops in Scala.

1. While Loop helps in repeating the statement or group of the statement when the condition comes out to be true, this way, it tests the conditions before the execution of the Loop body.
2. Do-While helps in testing the condition at the end of the Loop body.
3. For, helps in executing a sequence of statement number of times and abbreviates the code that manages in the Loop variable.
4. Break acts as a Loop control statement that terminates the Loop statement and transfers the execution to the statement that soon follows the Loop.

Question: What is an Infinite Loop?

Answer: An Infinite Loop appears when a condition never becomes a false statement.

Question: What are the different String Methods?

Answer: There are five different String Methods which include,

String trim(): It returns the copy of the string with leading and trailing of the whitespace omitted.

1. String to Uppercase: It converts all of the features in the String to the Uppercase using the given Locale rules.
2. Char[] to CharArray(): It converts the string to a new character array.
3. String[] split(String regext): It splits the string around the matches of the given regular expression.
4. Int length(): It returns the length of the string.

Question: Define Map in Scala?

Answer: A Map in Scala is the collection of key or value pairs that helps in retrieving a Value-Based on its key.

Question: What is Pattern Matching in Scala?

Answer: Pattern Matching in Scala consists of various sequences of alternatives that start with the Keyword case. Each of the alternatives available uses Pattern and Expressions. Scala evaluates these Patterns when they match, and the arrow symbol "=>" is used to separate it from the expressions.

Question: What is an Extractor in Scala?

Answer: An Extractor in Scala is referred to as the Object. It applies a method called "Unapply” on its members for the purpose of matching the value and take it apart.

Question: Define Auxiliary constructor and Que?

Answer: An auxiliary constructor is used for Constructor Overloading. It needs to call either previously defined or primary constructor in the first line of its body.

A queue is a data structure that is just like the Stack. However, its additional feature is that it follows First In First Out procedures for data processing. To apply Queues, you need to import a library called import scala.

Collection.mutable.Queue.

Conclusion

After going through the above question and answers carefully, it is advised to contact a friend and have a question and answer session with them. This way you can ask questions to your friend and the answer comes from the other side. The same pattern can continue for quite long. With this procedure, you will find that now have gained confidence in answering and could face Scala interview questions with courage. 

Here is a good Scala course to help you prepare for the interview: Scala & Functional Programming for Beginners | Rock the JVM.

Prepare for popular interview questions with this book: Cracking the Coding Interview: 189 Programming Questions and Solutions.

A smiling face and a confident answer is the key to crack an interview and accomplish success. It is therefore suggested to work sincerely on all the academic parts, take up the interview questions, prepare yourself to give a prompt reply, and face the Scala interview with courage. There is nothing impossible to accomplish in life and, therefore, the go-ahead for your Scala interview with courage and determination to succeed. Remember that the hiring manager is not only looking for correct answers, but a suitable person who is sincere and committed to his work, and along with that has the confidence level good enough to tackle all kind of situations in his job position. To accomplish these skills and achieve up to the expectations of the hiring manager to be ready to give an interview assertively.

Do you have any further tips to share? Or have any other questions that you came across in your interview? Share and comment below to help other fellow candidates!

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