What is Kotlin used for?

Kotlin is a modern, statically typed programming language known for its concise syntax, null safety, and strong interoperability with Java. While it first gained popularity for Android development, Kotlin has evolved into a versatile language used across various domains—from server-side applications to data science. Below, we explore its main use cases and why developers choose Kotlin for their projects.

1. Android App Development

Kotlin is Google’s preferred language for building Android apps, offering:

• Concise Code: Less boilerplate than Java, leading to fewer errors.
• Null Safety: Helps avoid the notorious NullPointerException.
• Seamless Interoperability: Kotlin works harmoniously with Java libraries, so you can mix both in the same project.

Example:

class MainActivity : AppCompatActivity() {
    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(R.layout.activity_main)
        
        // Kotlin's concise syntax
        findViewById<TextView>(R.id.helloTextView).text = "Hello from Kotlin!"
    }
}

As Android Studio fully supports Kotlin with features like smart completion and refactoring tools, most modern Android projects either start with Kotlin or migrate to it for more readability and fewer bugs.

2. Server-Side (Backend) Development

Beyond Android, Kotlin is also used on the backend:

• Ktor: A Kotlin-native framework for building REST APIs and microservices.
• Spring Framework: Seamlessly supports Kotlin, so developers can leverage Kotlin’s concise syntax while benefiting from the robust Spring ecosystem.

Advantages:

• Coroutines: Offers a non-blocking way of writing asynchronous code, ideal for high-performance web servers.
• Type Safety: Minimizes runtime errors by catching issues at compile time.

3. Cross-Platform & Multiplatform Projects

Kotlin Multiplatform allows code sharing across different platforms, including:

• Android & iOS: Write common business logic once, and have platform-specific UI layers.
• Desktop & Web: Kotlin/JS (compiling to JavaScript) and Kotlin/Native (compiling to machine code) let you target browsers and desktop systems.

While not as widespread as React Native or Flutter for cross-platform UIs, Kotlin Multiplatform excels in sharing logic modules (e.g., data models, networking code) across devices.

4. Scripting and CLI Tools

Kotlin’s scripting capabilities enable quick automation and command-line tools:

• Scripts: Write .kts (Kotlin scripts) for tasks like build automation, file manipulation, or quick prototypes.
• Integration: Easily integrates with Gradle, one of the most popular build tools in the JVM ecosystem.

5. Data Science and More

Though not as dominant as Python or R in data science, Kotlin is gaining traction:

• Libraries & Frameworks: Projects like KotlinDL for machine learning, or TornadoVM for GPU acceleration on the JVM.
• Notebook Support: Tools like Jupyter and Apache Zeppelin now have Kotlin kernels, fostering an interactive data exploration environment.

6. Why Developers Love Kotlin

1. Readability & Maintainability: The language design prioritizes clear syntax and safe defaults, making large codebases easier to manage.
2. Coroutines for Concurrency: Simplifies asynchronous operations without deeply nested callbacks.
3. Tooling & Community: Excellent IDE support (especially in IntelliJ IDEA and Android Studio) and an active community that contributes libraries, plugins, and best practices.

7. Strengthening Your Kotlin & System Design Skills

Whether you’re new to Kotlin or looking to refine your coding patterns, a solid grounding in algorithms, data structures, and system design enhances your ability to build robust software. Here are some recommended courses:

• Grokking the Coding Interview: Patterns for Coding Questions
  Perfect for mastering essential coding patterns and problem-solving—skills you can apply directly in Kotlin or any language.

• Grokking System Design Fundamentals
  Understand how large-scale applications are architected. Crucial for designing high-performance server-side services in Kotlin.

• Grokking the System Design Interview
  Ideal if you’re aiming for advanced discussions around scalability, distributed systems, and microservices—common topics for senior roles that involve Kotlin backend or cloud services.

8. Conclusion

Kotlin initially rose to fame for Android development, thanks to its clean syntax and Google endorsement. However, its usefulness extends far beyond mobile—powering server-side apps, cross-platform solutions, CLI tools, and even data science projects. By leveraging Kotlin’s modern features (like null safety and coroutines) alongside a strong foundation in coding patterns and system design, developers can create robust, scalable, and maintainable software across multiple domains.