If you are going to attend a Kotlin interview, then it is a must for you to have an idea about kotlin and what type of questions will be asked commonly in a Kotlin interview. I have come up with the best Kotlin interview questions and answers which helps you to get a job.

Kotlin interview questions and answers

Q1) What is Kotlin?

Ans: Kotlin is the latest general-purpose programming language from JetBrains with the type interference. It is totally interpolated with the JVM and also combines javascript or code.

Google officially promoted kotlin on Android for mobile development.  Kotlin is considered as a substitute to the standard java compiler.

Q2) Why kotlin is better than Java?

Ans: Kotlin is a simple general-purpose language, in which there is a code redundancy when compared to java. There are many features in kotlin like null safety, extension functions, primary constructors, inline or lamda expressions, properties and type interference for the properties and variables.

Q3) Explain about functions in kotlin?

Ans: Functions used in kotlin are simple to store in data structures and variables and can possess arguments which are passed from the high ordered data functions.

 An example of the sample function declaration in kotlin:

function double(y:int): 
    return 3 * y
val reslt = double(3)
Q4) What are the high order functions?

Ans:  High order functions consider functions as a parameter and produce a function.

Q5) How to convert a String into an int in the kotlin?

Ans: To convert a string value to the string value to it in kotlin we use point() method.

Let us see an example: 

function main(args: array) 
    val s: str]ng = "Kotlin"
    var y = 10
    y = "10".toint()
Q6) How to declare a variable in kotlin?

Ans: Declaration of a variable in kotlin is done by Val and var followed by data type.

val s: String = "Hello"
var Z = 5
Q7) What is the difference between Val and var in the declaration of variables?

Ans: The variables in Val declaration we can not reassign the variables, whereas in var declaration, the variables can be reassigned but the value reassigned should be the same type.

Function main(args:  array<string>)
val  s:  sting =  "Hello"
var  z  =  5
z  =  "6".
Q8) List out the basic data types we use in kotlin?

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Ans: Data type of a constant or a variable decides what is the type of a variable and how much space need to store. Types of data that a string allow are:

  • Strings
  • Numbers
  • Arrays
  • Booleans
  • Characteristics
Q9) How many types of constructors used in a kotlin?

Ans: Two basic types of constructors are involved in kotlin are:

Primary constructors: In this section, the header of the class is declared after the class name.

Secondary constructor: in this section, the constructor is declared in the body of the class. 

Moreover, we can add constructors for a class.

Q10) What is Null safety?

Ans: Null safety feature helps for the exception of null pointers in the expressions. It helps mostly in finding nullable and non-nullable references. We can thread null pointers by using nullable types like int? float? String?

var  int:   int? =  " sourcepoint.com"
var newint  = int?:  "default value"
int  = nill
new int  =int?: "default value"
Q11) What are the structural expressions in kotlin?

Ans: The three important structural expressions in kotlin are:

  • Break: break expression helps to break the closest enclosing loop
  • Return: This expression helps to return from the closest functions or default functions.
  • Continue: This expression helps to proceed for the next loop. 
Q12) Is there any chance to shift the code from java to kotlin?

Ans: We can shift the code which is used in the java to koltin by using JetBrains Idea.

Q13) What is mean by data lasses in koltin?

Ans: In java to store data items, we create a class by setting the variables. The setters and gathers are override to hash(), tostring(), and copy() functions. 

Whereas in kotlin, we need to add just the keyword data to the class, and everything remained is done automatically by default.

data class company(var  name: string)

Function main(args  array<string>)
Val company= company("Manhas Industries")
Q14) What are the available modifiers in kotlin?

Ans: Modifiers are the developers to personalize the declarations. There are four modifiers available in the kotlin, they are:

  • Public: By default, all the declarations are visible everywhere
  • Internal: This modifier helps to use declarations anywhere in the module.
  • Private: By this modifiers, the declarations are contained only in the file which is restricted.
  • Protected: In this, the declarations are secured, and not available for top-level declarations.
Q15) What type of programming does a kotlin accept?

Ans: Kotlin accept two types of programmings, they are:

  • Object-oriented programming
  • Procedural programming
  • Functional
Q16) How many types of strings are available in kotlin?

Ans: A collection of characteristics together is known as a string. There are two types of strings available in the kotlin:

  • Raw string 
  • Escaped string 
Q17) What is mean by string interpolation?

Ans: We can evaluate string templates in kotlin string. This template creation is known as string interpolation.

Q18) What we use in replacement to switch statement in kotlin?

Ans: We use when in kotlin in place of the switch in java

 case1: code executed if x=1:
case2: code  executed fi x=2:
Default code executed if x does not match any case
Q19) Is New a keyword in kotlin?

Ans: “New” is not a keyword in kotlin. We can initiate a new class as follow:

class  x
var  x  =  x()
val  new = x()
Q20) What is mean by init block?

Ans: Init is a login block and it is executed in the primary constructor and initialised. If you want to revoke in the secondary constructor then it starts working after primary constructor in the chain form.

Q21) Is inheritance compile in Kotlin?

Ans: Formal inheritance structure does not compile in the kotlin. By using open modifier we can final classes.

open  class B
class  c = B()
Q22) What is the Ranges Operator?

Ans: Ranges operator helps to iterate a loop with range.


for(i  1...15)

print (i)
Q23) How to compare two strings in kotlin?

Ans: We can compare two strings in two ways, 

Using”==” operator”.

Using compare() function
Q24) What are the class members in kotlin?

Ans: A class in kotlin have the following members:

  1. Initializer blocks
  2. Properties
  3. Open declarations
  4. Nested  classes
  5. Inner classes
Q25) List out some of the extension methods in kotlin?

Ans: Some of the extension methods are:

  • read Text(): Helps to read content in the files to a single string.
  • buffer Reader(): It is used to read contents of the file to buffer reader
  • read each line(): It reads each line by line in the file
  • readlines(): It helps to read lines of file for listing
Q26) How to handle a null operator?

Ans: By using Elvis operator we can handle all the nullable values.