Kotlin Interview Questions

Kotlin Interview Questions

Kotlin was introduced in 2011 by JetBrains, who were using Java earlier. There were two reasons for creating Kotlin, first and foremost is productivity. While the second one is the technology that demands evolution each day, which results in coding for the developers also needing some abstraction. The Kotlin Programming Language is an abstraction of Java with the core principles like Readability, conciseness, safety and ability to tool the language. The goal behind the development of Kotlin was to create an industry language that is used to develop a desktop, web server or mobile application so that Kotlin can be used in any application. Kotlin focuses on efficiency and dealing with the clutter of software development; adding up on that is now it is officially adopted as a supported language by Android. This has left the companies to look for a candidate with the knowledge of Kotlin. So, below are a few Kotlin Interview questions that will provide you with the overall structure of Kotlin, its components, and other basics. These questions might help you crack the interview with ease and get your hands on the job.

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Kotlin Interview Questions

It is an open source programming language that combines object-oriented programming features.
The features like Range Expression, Extension Function, Companion Object, Smart casts, Data classes are considered to be surplus of the Kotlin Language.
JVM, which stands for Java Virtual Machine is a feature of Kotlin. This feature compiles a Kotlin code into a native code, which can be done without JVM too.
Kotlin eases the coding process as it is simpler than Java and has many features required, that is not provided by Java yet like Extension functions, Null Safety, range expressions etc.
In Kotlin, we code approximately 40% less number of code lines as compared with Java.
In Kotlin, the Null safety is used to eliminate the risk of countering the NullPointer exception in real time.

Kotlin functions are first-class functions that are easily stored in variables and data structures and can be pass as arguments and returned from other higher-order functions.

Sample function declaration and usage in Kotlin

fun double(x: Int): Int {
    return 2 * x
val result = double(2)
The Kotlin program once compiled, can run on standard JVM like other programming codes.And, like many other programming languages main() function is the entry point of the Kotlin.
In programming, we use classes to hold data and these classes are called as data classes.
An object can be initialized in the data class and to access the individual parameters of these data classes, we use component functions.

In Kotlin a variable declared using val keyword is cannot be changed. It is similar to the final modifiers in Java whereas the variables declared using var keywords can be reassigned.

Val: Val, which is the short form of value, is a constant and it cannot be changed once assigned.
Var: Var, which is the short form of variable, is a storage location that accepts the reassignment of values that have the same data types.

toInt() method is used to convert a string value to integer or INT in Kotlin. Below is example uses

fun main(args: Array) {
    val s: String = "Kotlin"
    var x = 10
    x = "8".toInt()

Kotlin supports only two types of programming, and they are:
  • Procedural programming
  • Object-oriented programming
There are two types of constructors in Kotlin:
  • Primary constructor: It is a section of the Class header and is declared after the class name.
  • Secondary constructor: This constructor is declared inside the body.

Note: There can be more secondary constructors for a class.

Higher-Order Functions: A higher-order function is a function that takes functions as parameters, or returns a function.

Data types of a constant or variable decide what type of variable it is and how much space is required to store it.
The basic data types in Kotlin are:

  • Numbers
  • Characters
  • Strings
  • Arrays
  • Booleans
There are three Structural expressions in Kotlin.They are:
  • Return: It returns from the nearest enclosing function or anonymous function by default.
  • Break: This expression terminates the closest enclosing loop.
  • Continue: This expression proceeds you to the next closest enclosing loop.