What is Kotlin and what is it used for?

Introduction

Kotlin is a programming language created by JetBrains. Released in 2011, Kotlin’s developers aimed to create a Java-compatible language that would be more concise and productive. Google actively promotes Kotlin, providing official documentation and tooling. In 2024, Kotlin entered the top 20 most popular programming languages ​​for the first time, according to TIOBE.

Benefits of Kotlin for Android

Kotlin is considered the programming language of choice for Android. When choosing between Java and Kotlin for Android development, many choose JetBrains’ language, as it addresses many of Java’s weaknesses. Kotlin also boasts the following advantages:

• Conciseness. Kotlin allows developers to significantly reduce the amount of code they write compared to traditional Java. Tasks that previously required dozens of lines of programming can now be implemented in just a few lines, while maintaining high readability and logical structure.
• Compatibility with the Java ecosystem. A key feature of Kotlin is its full integration with the Java Virtual Machine (JVM). Developers can freely use the entire toolkit of Java technologies, including libraries, frameworks, and existing software solutions. Furthermore, Kotlin eliminates many of Java’s shortcomings, such as verbosity and frequent null-related errors.
• Enhanced safety system. One of Kotlin’s revolutionary technical solutions is the concept of Null Safety. This mechanism eliminates the possibility of critical NullPointerException errors, a persistent problem for Java developers. Code is protected from incorrect handling of uninitialized variables, significantly increasing software reliability.
• Flexibility and extensibility. Kotlin provides the ability to extend the functionality of existing classes through extension functions. Developers can add new methods to existing classes without changing the source code. This approach makes code more modular, easier to understand, and easier to maintain.
• Multithreading. Coroutines are an asynchronous programming tool. They enable efficient parallel computation, significantly optimizing application performance.

Where is Kotlin used?

Let’s look at the main areas where Kotlin is often used.

1. Mobile solutions

Following its official recognition by Google in 2019, Kotlin became the standard language for Android development. Mobile apps built with Kotlin are characterized by high performance and reliability. Furthermore, Kotlin is actively used in cross-platform development, allowing for the creation of a single codebase for both iOS and Android platforms.

2. Web development

The Kotlin programming language is also used in server-side development. Thanks to its compatibility with Java, developers can integrate popular frameworks such as Spring Boot and the modern Ktor, which is specifically designed for Kotlin.

3. Frontend and scientific research

Thanks to its compilation to JavaScript, Kotlin is successfully used for front-end development. In the scientific field, Kotlin is supported in Jupyter Notebook, opening up broad possibilities for data analysis and scientific computing. Integration with Java libraries provides additional tools for data processing.

4. Corporate solutions

Major tech companies, including Netflix, Pinterest, and Trello, are actively adopting Kotlin in their software products. The language’s stability, simplicity, and broad functionality make it ideal for enterprise development.

Kotlin development environments

There are several suitable development environments for Kotlin:

• IntelliJ IDEA. The official integrated development environment from the creators of Kotlin. It offers:
  • support for all language features;
  • refactoring tools;
  • integration with dependency management systems;
  • expansion of functionality through plugins.
• Android Studio. The official Android development environment with full Kotlin support. Includes:
  • visual interface editing tools;
  • Android emulator;
  • performance analysis tools.
• Eclipse. A Java development environment with a Kotlin plugin, although it lacks the functionality of IntelliJ IDEA and Android Studio.
• Visual Studio Code. A text editor with Kotlin support via specialized plugins, ideal for small projects.

Each of the presented environments has its own advantages and is suitable for different tasks and developer preferences. For large-scale projects, it’s best to choose the official products from IntelliJ and Android Studio, while smaller projects can be created using a text editor.

Basics of Kotlin Syntax

Kotlin’s syntax is concise and intuitive, significantly simplifying the development process. Here are its key elements.

Declaring variables

Kotlin supports two keywords for declaring variables:

• val— used for immutable variables (similar to final in Java).
• var— used for mutable variables.

val immutableVariable: String = "Hello, Kotlin" // Can't change
var mutableVariable: Int = 42                 // Can be changed
mutableVariable = 50

The data type can be specified explicitly or omitted, as Kotlin supports type inference:

val inferredType = "Type inferred as String"

Functions

A function declaration begins with the keyword fun.

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

If the function is one line, you can use the short form:

fun greetShort(name: String) = "Hello, $name!"

Conditional operators

Conditionals in Kotlin are simplified and can return a value:

val max = if (a > b) a else b

Cycles

Kotlin supports standard loops such as for, while, and do-while.

Example of using a loop for:

for (i in 1..5) {
    println(i) // Displays numbers from 1 to 5
}

Cycle through the collection:

val items = listOf("Apple", "Banana", "Cherry")
for (item in items) {
    println(item)
}

Null Safety

Kotlin prevents errors related to null. To work with variables that can be null, use the operator ?:

val nullableString: String? = null
val length = nullableString?.length ?: 0 // Elvis operator (if null, returns 0)

Classes

A class declaration in Kotlin looks like this:

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

Example of use:

val person = Person("John", 30)
println(person.name) // John
person.age = 31

Extension functions

Kotlin allows you to add functions to existing classes:

fun String.addExclamation(): String {
    return this + "!"
}
println("Hello".addExclamation()) // Hello!

Coroutines

Coroutines make it easier to work with asynchronous code:

import kotlinx.coroutines.*

fun main() = runBlocking {      // Launching a coroutine in a blocking context
    launch {     // Launching a new coroutine
        delay(1000L)     // Simulating a long-running task
        println("Hello from coroutine!")
    }
    println("Hello from main!")
}

Conclusion

Kotlin is a modern mobile development language that is also used for web and server development. Kotlin is characterized by its flexibility, conciseness, and support from major corporations. The programming language will likely continue to grow its community in the future.

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