Mansi Vaghela
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Kotlin Keywords

Kotlin Keywords

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Mansi Vaghela
·Apr 26, 2023·

3 min read

Kotlin is a modern programming language that was first introduced by JetBrains in 2011. Since then, Kotlin has gained a lot of popularity among developers due to its concise syntax, null safety, and interoperability with Java. One of the most important aspects of any programming language is its keywords. Keywords are reserved words that have a special meaning in the language and cannot be used as identifiers or variable names. In this blog, we will discuss some of the most important keywords in Kotlin.

val and var

In Kotlin, variables can be declared using either val or var. The val keyword is used to declare immutable variables, which means that their value cannot be changed once they are assigned. On the other hand, the var keyword is used to declare mutable variables, which means that their value can be changed.

val name = "John" // immutable variable
var age = 25 // mutable variable

if and else

The if and else keywords are used for conditional statements in Kotlin. They work in a similar way as in other programming languages. The if statement is used to check a condition, and if the condition is true, the code inside the if block is executed. If the condition is false, the code inside the else block is executed.

val num = 10
if(num > 0){
    println("Positive number")
    println("Negative number")


The when keyword is used for making decisions based on multiple conditions. It works like a switch statement in other programming languages. You can provide multiple cases and their corresponding actions using the when keyword.

val num = 2
    1 -> println("One")
    2 -> println("Two")
    3 -> println("Three")
    else -> println("Invalid number")


The fun keyword is used to define functions in Kotlin. Functions are a group of statements that perform a specific task. You can define a function with or without parameters.

fun greet(name: String){
    println("Hello, $name!")

class and object

In Kotlin, class and object are used to define data types. A class is a blueprint for objects, while an object is an instance of a class. You can define properties and functions inside a class, and then create objects of that class to access those properties and functions.

class Person(val name: String, var age: Int)

val person = Person("John", 25)
println( // John

person.age = 30
println(person.age) // 30


The return keyword is used to return a value from a function. It is also used to exit a loop or a block of code early.

fun add(num1: Int, num2: Int): Int{
    return num1 + num2
val result = add(5, 3)
println(result) // 8

In conclusion, Kotlin has a set of powerful and easy-to-use keywords that make it an excellent programming language for developers. The keywords we have discussed in this blog are just a few of the many that Kotlin offers, but they are essential for understanding the language's fundamentals. If you're interested in learning more about Kotlin, you can explore the official documentation and start building your own applications.

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