Kotlin Programming Language

Kotlin Programming Language

Intro to Kotlin

Kotlin is a statically typed programming language developed by JetBrains, the company known for creating the IntelliJ IDEA, a powerful IDE for Java development. Designed to interoperate fully with Java, and the JVM version of its standard library, Kotlin provides many improvements over Java, enhancing productivity, safety, and operationality. It’s an open-source language that has gained popularity in recent years, particularly in Android app development due to Google declaring it a preferred language for Android.

Quick Facts about Kotlin

  • Official Language for Android: In 2019, Google announced Kotlin as a preferred language for Android app developers, increasing its popularity and adoption.
  • Rapidly Growing: According to the 2021 Stack Overflow Developer Survey, Kotlin is one of the most loved languages and is rapidly growing in popularity among professional developers.
  • Interoperability: Kotlin is 100% interoperable with Java, meaning developers can leverage all existing Java libraries, frameworks and tools while enjoying the benefits of a modern language.
  • Null Safety: Kotlin aims to eliminate the null reference exception from code by incorporating inherent null safety, a feature that is highly appreciated by developers.
  • Coroutines Support: Kotlin has built-in support for coroutines, enabling developers to write asynchronous code more easily and intuitively. This helps improve the readability of code and makes it less prone to errors.

History and Development of Kotlin

Kotlin was first unveiled by JetBrains in July 2011, with the aim of addressing some of the issues the team encountered with other languages they were using. The name Kotlin originates from Kotlin Island, near St. Petersburg, Russia. The project was born out of the need for a more expressive and less verbose language than Java that could fully interoperate with it. The first official stable release, Kotlin v1.0, was made public in February 2016.

Strengths of the Kotlin Language

Kotlin is popular among developers because of its modern, expressive syntax that makes code more readable and understandable. It supports both object-oriented and functional programming paradigms, making it highly versatile for a variety of coding styles and applications. Null safety is a built-in feature of Kotlin’s type system, helping to eliminate the dreaded NullPointerException from your code. It also provides coroutines, which are a powerful feature for writing asynchronous code in a more sequential style, making it easier to read and understand.

Kotlin’s interoperability with Java makes it a seamless transition for Java developers, allowing them to use existing Java libraries and frameworks in Kotlin projects, thereby leveraging the vast ecosystem of Java while enjoying the benefits of a modern language. With these features, Kotlin offers a blend of simplicity, power, and flexibility that has led to its rapid adoption in the software development world.

Why Choose Kotlin?

Kotlin is a versatile and efficient language preferred for its interoperability with Java, less verbose syntax, null safety, and support for coroutines. Its unique features like extension functions, smart casts, default arguments, and named parameters enhance coding efficiency and readability. Kotlin is favored for a range of software development projects, from Android app development and server-side applications to data science, making it an excellent choice for developers seeking a comprehensive, modern, and type-safe language.

Kotlin Advantages Over Other Languages

Kotlin’s advantages are many and varied, making it a preferred choice over other programming languages in certain contexts. Its most significant benefits emerge when comparing it with its closest alternative, Java, especially in the realm of Android app development. Kotlin’s concise and expressive syntax reduces boilerplate code, making it faster to write and easier to read. This increased readability contributes to more maintainable and less error-prone code.

Kotlin also features null safety, reducing the infamous null pointer exceptions that are so common in Java, thereby reducing application crashes and improving system stability. Additionally, Kotlin’s support for both object-oriented and functional programming paradigms allows developers to choose the most suitable approach for a given problem.

In the Android development ecosystem, Kotlin has become a go-to language. Google’s official support has led to rapid adoption by developers, resulting in many existing Java Android apps being rewritten in Kotlin. Moreover, the interoperability of Kotlin with Java means developers can still use all the familiar Java libraries and frameworks while benefiting from Kotlin’s more modern syntax.

In the wider software development field, the features of Kotlin are gaining recognition. Its efficient syntax, inherent safety features, and compatibility with existing Java codebases make it an appealing choice for backend development and data science tasks.

For instance, JetBrains, the company behind Kotlin, uses the language extensively in its own software products. Gradle, a leading build automation system, also adopted Kotlin as a language for writing build scripts. Furthermore, many enterprises are opting for Kotlin for building server-side applications, drawn by its expressive syntax and the robust tooling inherited from Java.

Whether you are an Android developer looking to leverage the modern features of Kotlin for app development or a software engineer interested in a more expressive and safer language for backend development, Kotlin might be the right choice for your next project.

Unique Features of Kotlin

  1. Extension functions: Kotlin allows developers to extend a class with new functionality even without inheriting from the class.
  2. Smart casts: The Kotlin compiler tracks the logic of the code and auto-casts types if possible, reducing the amount of explicit casts that developers need to write.
  3. Default Arguments and Named Parameters: This feature allows developers to set default values for function parameters and pass arguments by name, rather than by index.

Where Kotlin Excels

  1. Android development: Given its interoperability with Java and the powerful features it offers, Kotlin has been officially adopted by Google for Android app development.
  2. Server-side development: Kotlin’s concise syntax, expressiveness, and safety make it a great choice for server-side development.
  3. Data Science: Kotlin is a statically typed language that also provides an interactive shell similar to Python’s, which makes it a suitable candidate for data science and machine learning tasks.

Kotlin is an excellent choice for a variety of software development projects, whether it’s for building mobile apps, developing server-side applications, or even doing data analysis.

Getting Started With Kotlin

If you’re interested in learning how to write code with the Kotlin language, this section should help you out with that goal. We’ll explain the process of getting up and running with your first Kotlin code.

System Requirements

To run Kotlin, all you need is a computer capable of running IntelliJ IDEA or Android Studio. Here are the minimum system requirements:

  1. Microsoft Windows: Windows 7/8/10 (64-bit) with minimum 2GB RAM, 3 GB recommended.
  2. macOS: Mac OS X 10.8.3 or higher, also with a minimum of 2GB RAM, 3 GB recommended.
  3. Linux: Any modern distribution capable of running the latest versions of IntelliJ IDEA.

Installation and Setup

The best way to get started with Kotlin is to download and install IntelliJ IDEA. JetBrains, the creators of Kotlin, also created IntelliJ IDEA, so it’s no surprise that Kotlin has first-class support in this IDE.

Here’s a step-by-step guide on how to get started:

  1. Download and install IntelliJ IDEA from JetBrains’ official website. Choose the Community Edition, which is free.
  2. Open IntelliJ IDEA and create a new project. Select Kotlin/JVM.
  3. Choose your project’s location, name, and JDK (Java Development Kit). Click on ‘Finish’ to create the project.

Hello World! Example

Now that you have set up your IDE, it’s time to write your first Kotlin program. Create a new Kotlin file in your project, name it ‘Main.kt’ and copy the following code into it:

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

This code declares a main function (the entry point to the program), which prints the string “Hello, World!” to the standard output.

Integrated Development Environments (IDEs) and Tools

While IntelliJ IDEA is the most popular choice, there are other IDEs and tools that also support Kotlin:

  1. Android Studio: Since Kotlin is officially supported by Google for Android development, Android Studio comes with built-in Kotlin support.
  2. Eclipse: With the Kotlin Plugin for Eclipse, you can also develop Kotlin applications in Eclipse.
  3. Command Line: Kotlin can be compiled and run from the command line using the Kotlin compiler.
  4. Online Playgrounds: JetBrains provides an online playground where you can experiment with Kotlin in a web browser without needing to install anything.

Development Tools

n addition to IDEs, there are many tools that can help you in developing Kotlin applications:

  1. Ktor: A framework for building asynchronous servers and clients in connected systems.
  2. Gradle: A build system that allows you to write your script in Kotlin.
  3. Detekt: A static code analysis tool for the Kotlin programming language.
  4. Kotlin/JS: Allows you to transpile your Kotlin code, the Kotlin standard library, and any compatible dependencies to JavaScript.

The next step is to learn the basics of the language. Once you’ve got your environment set up, you’re ready to dive into Kotlin’s syntax, data types, and basic operations.

Kotlin Language Basics

Let’s take a look at the basic elements of the Kotlin programming language, including syntax, variables, and other aspects of the fundamentals of Kotlin.

Kotlin Syntax

Kotlin’s syntax is clear and concise, which makes the language easy to read and write. A simple function in Kotlin might look like this:

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

In this example, fun is used to declare a function. name is a parameter of type String, and the function returns a String. The $name inside the string is a string template that inserts the value of name.

Variables and Data Types

Variables in Kotlin can be read-only (declared with val) or mutable (declared with var). For instance:

val message: String = "Hello, Kotlin"
var counter: Int = 0

Kotlin has rich set of built-in data types including Int for integers, Double for floating point numbers, Boolean for truth values, and String for text.

Control Flow

Control flow structures in Kotlin are similar to other C-like languages. It supports if, when (analogous to switch), for, while, and do-while loops.

Null Safety

One of Kotlin’s key features is null safety. Kotlin types are non-nullable by default, which means that Kotlin code won’t compile if there’s a possibility of a null reference, thus saving you from potential NullPointerExceptions.

Classes and Objects

Kotlin is fully object-oriented. You can declare classes with the class keyword. To create an instance of a class, you call the constructor as if it were a regular function (no new keyword is required).


Functions in Kotlin are declared with the fun keyword. Kotlin supports local functions, member functions, function literals with receiver, extension functions and infix functions.


Kotlin has powerful support for collections, such as lists, sets, and maps. You can create them easily:

val numbers = listOf(1, 2, 3, 4, 5)

Once you understand the basics, it’s easier to dive deeper into more advanced Kotlin features such as coroutines for asynchronous programming, extension functions, destructuring declarations, and more.

Kotlin Advanced Concepts

Now that we’ve covered some of the basic principles for the Kotlin language, let’s move on to more advanced aspects of the langauge.

Object-oriented Programming

Kotlin supports classical object-oriented programming paradigms and improves upon them with the introduction of new concepts.

Classes and Objects: A class is defined using the keyword class. Kotlin also offers data classes, which are classes that only hold data. They automatically get equals(), hashCode(), and toString() generated.

class MyClass {
    // class body

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

Inheritance: Kotlin supports single inheritance, with all classes having a common superclass Any. By default, classes in Kotlin are final; they can’t be inherited from. To make a class inheritable, you need to mark it with the open keyword.

open class Base(p: Int)

class Derived(p: Int) : Base(p)

Interfaces: Kotlin interfaces can contain definitions of abstract methods and implementations of non-abstract methods.

interface MyInterface {
    fun bar()
    fun foo() {
      // optional body

Extensions: Kotlin provides the ability to extend a class with new functionality without having to inherit from the class or use any type of design pattern.

Functional Programming

Kotlin is also a fully functional language.

  1. Lambdas and Higher-Order Functions: Kotlin supports lambda expressions and higher-order functions – i.e., functions that can accept other functions as parameters and return them.
  2. Collections and Streams: Functional operations on collections like filter, map, reduce, etc., are easy and expressive in Kotlin.
  3. Null Safety: In the world of functional programming, nullability problems are typically handled with Option types. Kotlin handles it at the language level with nullable and non-nullable types.

Concurrency and Coroutines

Kotlin has first-class support for coroutines, which are used to simplify work with asynchronous programming and make the code easier to read and understand.

  1. Coroutines: Coroutines are a way of writing asynchronous code sequentially. Instead of using callbacks, you can suspend a coroutine, perform some asynchronous operation, and then resume the coroutine when the result is ready.
  2. Channels and Flows: Kotlin provides constructs like channels and flows to handle streams of data in an asynchronous fashion.

The more you work with Kotlin, the more you’ll appreciate its unique blend of OO and functional programming, enhanced with powerful features that make your code more reliable and expressive.

Popular Kotlin Apps and Tech Stack Integration

Kotlin is a language of choice for many developers and businesses worldwide. Several well-known applications and services have Kotlin in their tech stacks.

Apps Built with Kotlin

Kotlin Best Practices

Writing efficient and maintainable code requires understanding best practices for the language you’re using. Here are some recommendations for working with Kotlin.

Pinterest: Pinterest switched to Kotlin due to its null-safety compiler guarantees and concise language features, which they found helped increase developer happiness and efficiency.

Postmates: This popular American delivery service uses Kotlin for its innovative features and seamless interoperability with Java.

Coursera: This massive open online course provider employs Kotlin to benefit from its modern language features that boost productivity and developer satisfaction.

Kotlin in Tech Stacks

Kotlin plays well with other technologies and integrates seamlessly into various tech stacks.

Java: As a JVM language, Kotlin is completely interoperable with Java. Developers can even maintain both Kotlin and Java code within the same project.

Android: Kotlin is fully supported by Google for Android development, allowing developers to leverage all Android libraries and features while benefiting from Kotlin’s more modern, expressive syntax.

Spring: Kotlin works excellently with the Spring Framework. The Spring team has actively worked on delivering first-class support for Kotlin, offering things like null-safety and Kotlin extensions.

Kotlin’s modern features, interoperability with Java, and backing from Google and JetBrains make it a powerful player in the world of programming languages. Whether you’re developing an Android app or building backend services, Kotlin has a role to play in your tech stack.

Code Organization and Structure

  1. Use Packages: Leverage packages to organize your source files. Group related classes and files together in the same package to make your codebase easier to navigate.
  2. Naming Conventions: Use clear and descriptive names for classes, functions, and variables. This makes your code easier to read and understand.

Coding Conventions and Style Guides

Follow Kotlin’s official style guide for naming, formatting, and structuring your code. Key points include:

  1. Use camelCase for names (e.g., myVariable).
  2. Use KDoc for documentation.
  3. Avoid using raw types for complex structures.
  4. Keep your classes, methods, and functions short and focused.

Testing and Debugging

Kotlin’s Standard Library includes excellent tools for unit testing. Utilize them to ensure your code’s correctness. When debugging, use Kotlin’s built-in debugging tools which integrate with most IDEs.

Performance Optimization

While Kotlin is generally performant, some practices can help optimize your code further:

  1. Use when expressions instead of long if expressions.
  2. Use sequences for large data sets.
  3. Be aware of boxing and unboxing when using generic types.

Security Considerations

  1. Avoid null pointer exceptions by utilizing Kotlin’s built-in null safety.
  2. Be careful with the use of Kotlin’s !! operator. It can throw null pointer exceptions if not used correctly.

Following these best practices will not only make your Kotlin code more efficient and maintainable but will also improve your overall programming skills.

Learning Kotlin

Recommended Prerequisites

Before you start learning Kotlin, it’s helpful to have a basic understanding of programming principles and at least one other programming language. Knowledge of Java can be particularly useful, as Kotlin and Java are syntactically similar and inter-operable.

Online Tutorials and Courses

There are numerous online resources for learning Kotlin:

  1. Kotlin for Beginners: Learn Programming With Kotlin – This course on Udemy covers the basics of programming in Kotlin.
  2. Kotlin Bootcamp for Programmers – Google’s free course on Udacity is a fast-paced introduction to Kotlin for developers who are already familiar with programming concepts.
  3. Kotlin Koans – A series of exercises specially designed to get you familiar with the Kotlin Syntax.

Books and Publications

Several books offer in-depth instruction on Kotlin:

  1. Kotlin in Action – This book provides a detailed introduction to the Kotlin language for professional developers.
  2. Programming Kotlin – This book explores advanced Kotlin features and helps you understand how Kotlin works under the hood.

Practice Projects and Coding Exercises

Hands-on experience is crucial when learning a new language. Try to build simple applications or solve coding exercises. Websites like Codewars, LeetCode, or HackerRank have Kotlin support for their problems.

Tips for Effective Learning

Remember that consistency is key when learning a new language. Regular, focused practice will help you grasp Kotlin’s concepts and structures. Don’t rush through the materials; take your time to understand the concepts, and make sure to work on practical projects to apply what you’ve learned.

Career Outlook for Kotlin Developers

For those who are interested in developing with Kotlin, it’s also useful to know what the job market looks like. Here’s some information that should be useful for you as you consider a career using Kotlin.

Kotlin Job Market Trends

Kotlin’s growing popularity, particularly in Android app development, has led to an increase in demand for Kotlin developers. It is consistently ranked among the top languages developers are keen to learn, indicating a robust future job market.

Job Titles and Roles

Common job titles for Kotlin developers include Kotlin Developer, Android Developer, Full Stack Developer, and Mobile Application Developer. In these roles, developers often create and maintain Android apps, but they also work on back-end development, particularly when using frameworks like Ktor.

Salary Expectations

As of the time of writing, the average salary for a Kotlin developer in the United States is around $116,000 per year, but this can vary widely based on experience, location, and the specific demands of the position. Senior and specialized roles may command significantly higher salaries.

Industries and Sectors

Kotlin is used across a range of industries, with particular prominence in tech, finance, and e-commerce sectors. Large tech companies like Google, Atlassian, and Pinterest have adopted Kotlin, and its usage is expected to grow across industries.

Freelance and Remote Work Opportunities

There is a healthy market for freelance Kotlin developers, with opportunities to work on diverse projects worldwide. Websites like Upwork, Freelancer, and Toptal have numerous postings for Kotlin-related work. Furthermore, with the increase in remote work trends, Kotlin developers have more flexibility in choosing opportunities that suit their lifestyle and career goals.

Kotlin Community and Resources

The Kotlin community is very active, and there are

Official Documentation

The official Kotlin documentation, maintained by JetBrains, is a great place to start for those wanting to learn the language or find reference material. It provides a comprehensive guide to the language’s syntax, standard library, and features. You can access it here.

Online Tutorials and Courses

There are several online resources for learning Kotlin, ranging from beginner to advanced levels. Websites like Coursera, Udemy, and Codecademy offer courses on Kotlin. Google’s Android Developer website also offers free Kotlin training, considering its use for Android development.

Books and Publications

Several books offer in-depth study of Kotlin. Some popular ones include “Kotlin in Action” by Dmitry Jemerov and Svetlana Isakova, “Mastering Kotlin” by Nate Ebel, and “Kotlin for Android Developers” by Antonio Leiva.

Forums and Discussion Groups

Communities like Stack Overflow, Reddit’s r/Kotlin, and JetBrains’ own Kotlin Forums have active Kotlin categories where users discuss issues and share knowledge. Here you can get help with problems, stay informed about updates, and connect with other Kotlin developers.

Conferences and Meetups

Several conferences focus on Kotlin, including KotlinConf hosted by JetBrains. Local meetups, which can be found on platforms like Meetup.com, provide more informal settings to connect with other developers. Furthermore, most general programming and software development conferences have sessions on Kotlin.

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