TOP Scala Interview Questions and Answers

Read Latest Scala Interview Questions and Answers for Freshers, 2+ Years Experienced Q and A with Explanation PDF.

What is Scala?

Scala is an object functional programming and scripting language for general software applications designed to express solutions in a concise manner.

What is a ‘Scala set’? What are methods through which operation sets are expressed?

Scala set is a collection of pairwise elements of the same type.  Scala set does not contain any duplicate elements.  There are two kinds of sets, mutable and immutable.

What is a ‘Scala map’?

Scala map is a collection of key or value pairs.  Based on its key any value can be retrieved.  Values are not unique but keys are unique in the Map.

What is the advantage of Scala?

a)      Less error prone functional style

b)      High maintainability and productivity

c)       High scalability

d)      High testability

e)      Provides features of concurrent programming

In what ways Scala is better than other programming language?

a)      The arrays uses regular generics, while in other language, generics are bolted on as an afterthought and are completely separate but have overlapping behaviours with arrays.

b)      Scala has immutable “val” as a first class language feature. The “val” of scala is similar to Java final variables.  Contents may mutate but top  reference is immutable.

c)       Scala lets ‘if blocks’, ‘for-yield loops’, and ‘code’ in braces to return a value. It is more preferable, and eliminates the need for a separate ternary operator.

d)      Singleton has singleton objects rather than C++/Java/ C# classic static.  It is a cleaner solution

e)       Persistent immutable collections are the default and built into the standard library.

f)       It has native tuples and a concise code

g)      It has no boiler plate code.

What are the Scala variables?

Values and variables are two shapes that come in Scala. A value variable is constant and cannot be changed once assigned.  It is immutable, while a regular variable, on the other hand, is mutable, and you can change the value.

The two types of variables are

var  myVar : Int=0;

val   myVal: Int=1;

Mention the difference between an object and a class?

A class is a definition for a description.  It defines a type in terms of methods and composition of other types.  A class is a blueprint of the object. While, an object is a singleton, an instance of a class which is unique. An anonymous class is created for every object in the code, it inherits from whatever classes you declared object to implement.

What is recursion tail in scala?

‘Recursion’ is a function that calls itself. A function that calls itself, for example, a function ‘A’ calls function ‘B’, which calls the function ‘C’.  It is a technique used frequently in functional programming.  In order for a tail recursive, the call back to the function must be the last function to be performed.

What is ‘scala trait’ in scala?

‘Traits’ are used to define object types specified by the signature of the supported methods.  Scala allows to be partially implemented but traits may not have constructor parameters.  A trait consists of method and field definition, by mixing them into classes it can be reused.

When can you use traits?

There is no specific rule when you can use traits, but there is a guideline which you can consider.

a)      If the behaviour will not be reused, then make it a concrete class. Anyhow it is not a reusable behaviour.

b)      In order to inherit from it in Java code, an abstract class can be used.

c)       If efficiency is a priority then lean towards using a class

d)      Make it a trait if it might be reused in multiple and unrelated classes. In different parts of the class hierarchy only traits can be mixed into different parts.

e)      You can use abstract class, if you want to distribute it in compiled form and expects outside groups to write classes inheriting from it.

What is Case Classes?

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 values.


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