Kotlin Interview Questions

Kotlin 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 a surplus of the Kotlin Language.

In Kotlin, you can declare a variable using var or val which followed by an optional datatype.

Variable declaration in Kotlin looks like:

val s: String = "Hi"
var x = 5

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

• Procedural programming
• Object-oriented programming

• 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.

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.

Access modifier in Kotlin provides the developer to customize the declarations as per the requirements. Kotlin provides four modifiers. They are:
Private: This makes the declaration visible only inside the file containing a declaration.

Public: It is by default, which means that the declarations will be visible everywhere.

Internal: This makes the declaration visible everywhere in the same modules.

Protected: This keeps the declaration protected and is not available for top-level declarations.

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

• Raw string
• Escaped string

In Kotlin String, templates can be evaluated.This evaluation of string templates is called as the string template interpolation.

Kotlin is simple and easy to learn as its syntax is similar to that of Java.

It is the functional language that is based on JVM (Java Virtual Machine), which removes the boilerplate codes. Upon all this, Kotlin is considered as an expressive language that is easily readable and understandable and the performance is substantially good.
It can be used by any desktop, web server or mobile based applications.

Disadvantages:

Kotlin does not provide the static modifier, which causes problems for conventional java developer.

In Kotlin, the function declaration can be done in many places in the application, which creates the trouble for the developer to understand which function is being called.

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.

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 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)