Top Scala Interview Questions for Freshers

Introduction:

Welcome to the most useful article. Here you will find Top Scala Interview Questions for Freshers (2023). It will help to prepare for the interview.

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Top Scala Interview Questions for Freshers

1. What is Scala and what are its features?

Ans: Scala is a high-level programming language that runs on the Java Virtual Machine (JVM). It is a modern, functional, and object-oriented language that is designed to address the shortcomings of Java and other languages.

2. What is the difference between Scala and Java?

Scala and Java are both programming languages that run on the JVM, but they have several differences:

1. Syntax: Scala has a more concise and expressive syntax than Java. It uses features like operator overloading and implicit conversions to make code more readable and concise.
2. Type inference: Scala supports type inference, which means that the compiler can automatically deduce the type of a variable or expression. Java, on the other hand, requires explicit type declarations for all variables and expressions.
3. Functional programming: Scala has built-in support for functional programming, which allows you to write code that is more concise and expressive than traditional imperative code. Java has some support for functional programming, but it is more limited.
4. Immutability: Scala encourages immutability, which means that once a value is assigned to a variable, it cannot be changed. Java does not have the same level of support for immutability.

3. Explain the concept of Traits in Scala.

Ans: In Scala, a trait is a collection of methods and fields that can be mixed into a class to provide additional functionality. Traits are similar to interfaces in Java, but they can also include implementation code.

To define a trait in Scala, you use the trait keyword followed by the trait name and the implementation code. For example:

trait Greeter {
def greet(name: String): String = s”Hello, $name!”
}

4. What is the significance of ‘object’ in Scala?

Ans: In Scala, an object is a singleton instance of a class that is automatically created when the program starts. An object can have methods, fields, and other members just like a class, but it can only have one instance.

The object a keyword is used to define an object in Scala. For example:

object HelloWorld {
def sayHello(): Unit = {
println(“Hello, world!”)
}
}

5. What is the difference between var and val in Scala?

Ans: In Scala, var and val are keywords used to define variables? The main difference between the two is that var defines a mutable variable, while val defines an immutable variable.

A mutable variable can be changed after it is assigned a value, while an immutable variable cannot be changed once it is assigned a value. Here is an example:

var x = 5 // x is a mutable variable
x = 10 // we can change the value of x

val y = 5 // y is an immutable variable
y = 10 //This will result in a compile-time error

6. What is the use of Scala REPL?

Ans: Scala REPL (Read-Eval-Print Loop) is an interactive interpreter for the Scala programming language. It allows you to write and execute Scala code snippets in real-time, without the need to compile and run a separate program.

for ex:

scala> 1 + 2
res0: Int = 3

scala> “Hello, world!”
res1: String = Hello, world!

scala> List(1, 2, 3).map(_ * 2)
res2: List[Int] = List(2, 4, 6)

In the above example, we launch the Scala REPL and enter several Scala code snippets. Each snippet is evaluated and executed immediately, and the result is printed out on the next line of the REPL prompt.

7. What is pattern matching in Scala and how is it useful?

Ans: Pattern matching is a powerful feature of the Scala programming language that allows you to match values against patterns and extract data from them.

It is similar to the switch statement in Java or other programming languages, but with much greater flexibility and expressive power.

In Scala, pattern matching is done using the match keyword, and typically takes the form of a series of case statements, each of which defines a pattern to match against, and a corresponding expression to execute if the pattern matches. Here is an example:

val x: Any = “Hello” 

x match { 

case s: String => println(“Found a string: “ + s) 

case i: Int => println(“Found an integer: “ + i) 

case _ => println(“Unknown type”) 

}

8. What is the significance of ‘lazy val’ in Scala?

Ans: In Scala, a val is a variable that is assigned a value once and cannot be reassigned. A lazy val, on the other hand, is a value that is evaluated only when it is accessed for the first time, and then stored for later use.

lazy val expensiveData = {
println(“Loading expensive data…”)
// perform expensive computation or I/O here
List(1, 2, 3, 4, 5)
}

println(“Starting program…”)
println(“Accessing expensive data…”)
println(expensiveData)
println(“Done.”)

In this example, we define a lazy val called expensiveData that contains some expensive computation or I/O. When the program starts, the println the statement is executed immediately, but the expensiveData value is not yet evaluated.

9. What are higher-order functions in Scala?

Ans: In Scala, higher-order functions are functions that either take other functions as arguments or return functions as their result. Higher-order functions are a fundamental concept in functional programming and are commonly used in Scala to write concise and expressive code.

Here’s an example of a higher-order function in Scala that takes a function f and applies it n times to a given value x:

def applyNTimes(f: Int => Int, x: Int, n: Int): Int = {
if (n == 0) x
else applyNTimes(f, f(x), n-1)
}

val result = applyNTimes(x => x * 2, 1, 3)
println(result) 

// Output: 8

10. What is the difference between a function and a method in Scala?

Ans: In Scala, a function and a method are similar in that they both define a set of instructions that can be executed. However, there are some key differences between the two:

1. Syntax: A function in Scala is defined using the => operator, while a method is defined using the usual syntax for method definitions. For example:// Function definition
   val double: Int => Int = x => x * 2// Method definition
   def double(x: Int): Int = x * 2
2. Scope: A function in Scala is a first-class object that can be passed around and used as a value, just like any other object. A method, on the other hand, is defined as part of a class or an object and is therefore bound to that context.