What Is Kotlin? A Brief Introduction

Since the inauguration of Kotlin in 2011 by Jetbrain, it has made quite a name in the community of developers. Among all the statically typed and general-purpose languages, Kotlin stands on a higher ground comparing the most programming languages ​​to learn in this era of computer science.

But what exactly is it? Let’s take a deeper look.

What Is Kotlin?

Kotlin is a statically-typed programming language. It supports exiguous subtyping along with polymorphism and variance. At the same time, though, it manages to maintain higher-order functions and lambda literal syntax.

Kotlin also aids compilation platforms like JavaScript, Java Virtual Machine (JVM), and Native. Moreover, it grants compile time among nullable and non-nullable types obtaining null safety. For better interoperability, Kotlin extends its static type function with moderate and flow elements.

Coding in Kotlin

fun main() {
println("Hello World")

If you have written your first Kotlin code, you’ll notice the main() function declared as fun—an entry point of the Kotlin application and defines a block of code to perform a specific task.


This main() function also contains variables. Here is a fun fact about print() and println(). The print() function prints its arguments in standard output that is similar to the println() function but println() also adds a line break.

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Comments and Keywords in Kotlin

In Kotlin source code, a comment is an annotation that makes source code readable for programmers. Kotlin allows single and multi-line comments.

If you are thinking about Kotlin keywords, you should know that Kotlin uses predefined ones. Therefore, reserved keywords have special meanings to the compiler and cannot be used as an identifier.

Variables in Kotlin

Using the keyword var or val then equal to = sign, you can assign a value to create a variable.

var language ="Java"
val salary = 30000

Kotlin has two types of variables: mutual variable and read-only.

The mutable variable is a kind of variable that can reassign a different value using var after its initial assignment. On the other hand, the read-only variable is constant. You will use val to assign a read-only variable.

Kotlin Is an Object-Oriented Programming (OOP) Language

Another important characteristic of a programming language is the data type. As an OOP language, Kotlin defines everything as an object. Therefore, you can call the properties in any variable.

Kotlin has built-in operators, like it does with data types. Examples of these operators include Unary and Bitwise.

Related: Object-Oriented Programming vs. Object-Oriented Programming. Procedural Programming: What Makes Them Different?

Functions in Kotlin

As a statically typed language, functions and parameters play a significant role in Kotlin. As such, Kotlin features various built-in functions. It also allows a user-defined function that can take zero or multiple parameters.

In a Kotlin function, a return value depends on the requirement. If the function does not return its value, its type is unit. That means the unit-returning function contains a single value. Besides, if you want to calculate the factorial of a number, you can use a recursive function.

fun printHello(name: String?): Unit {
if (name != null)
println("Hello $MUO")
else println("Hi there!")
// `return Unit` or `return` is optional

Above all functions, Kotlin has two particular kinds of functions named Lambda function and Inline function.

Why Should You Learn Kotlin?

Like Java, Kotlin has become rapidly famous among developers. Even Google has announced Kotlin as their prime choice over Java on android development. From mobile development to web applications or devices, Kotlin is taking place over the board.

Learning Kotlin can aid you in knowing more about language design and show you some gaps in Java. Even if you are not willing to be a professional Kotlin developer, learning this language can empower you to become a master in other languages ​​like Go and Rust, Scala, and Swift, as they share some basic notions.

Kotlin’s Key Features

Kotlin has several important features, but we’ve listed some of the most important ones below.

Interoperability With Java

Kotlin’s one of the best features is its interoperability with Java. Kotlin itself runs on JVM supporting Java tools and libraries.

Lazy-Loading Feature

Any developer who wants to decrease their startup time can use lazy-loading features in Kotlin. This particular feature allows loading only the resources on the main memory which is needed.

Collection Filter

If you are working on the API, you may encounter collections repeatedly. In Kotlin, there is a collection filter feature that helps you to decide your resulting content.

Data Classes

In Kotlin, some classes primarily hold the data. However, these classes maintain some standard functionality and run a few utility functionalities that mechanically derive the data. Likewise, these are known as data classes in Kotlin and marked with data:

data class User(val name: String, val age: Int)

What Is Kotlin Used For?

The primary idea behind Kotlin is to make programming languages ​​more compatible with day-to-day app development—mostly on server-side or client-side to advanced Android development. However, Kotlin is versatile, and you can perform any development using it.

Programmers use Kotlin for server-side applications, as well as the mobile app. In addition to developing the backend, Kotlin uses JavaFX, JavaScript, and so on. You can use Kotlin in native development on any desktop or mobile platform, and even on some internet of things (loT) devices.

Which Companies Use Kotlin?

Kotlin is the official language for Android, announced by Google in 2007. Since then, infinite programmers from all over the world and disciplines have started using Kotlin as their development technology.

Another example of a company using Kotlin is Atlassian, which developed the Trello app for Android using this language. Similarly, Pinterest used Kotlin for its own Android app.

Related: How to Make Your Pinterest Boards Interesting

Evernote is another company to use Kotlin and switched from Java.

Is Kotlin a Java Alternative?

Kotlin is a more concise and streamlined edition of Java, but is interoperable with it; you can call any Java code from Kotlin and vice-versa.

One thing worth noting is that Kotlin is more type-safe than Java. So, you can be more adaptable when developing apps—and don’t need to worry about as many possible risks.

Kotlin removes one of the standard Java defaults on NullPointer Exception. Moreover, Kotlin supports designated properties—and it has relaxed Java’s requirement.

Kotlin: A Simple, Powerful Programming Language

Kotlin helps app developers streamline their workflows significantly while not needing to worry about their creations suffering as a result. Although it’s still relatively new in the world of programming, it has grown significantly in a short space of time—with several companies using it.

Learning Kotlin is a great idea if you want to advance your career as an app developer. Having read this guide, you should now have a basic understanding of what it is and how it works.

Illustration of Kotlin and java logos

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