Kotlin Use Cases with Example Source Code

Kotlin is a modern, open-source programming language that can be used for a wide range of applications, from mobile app development to server-side web development. Here are some common use cases for Kotlin, along with examples of source code to help you get started:

Android app development: Kotlin is a popular language for developing Android apps, either using Android Studio or other integrated development environments (IDEs). Here’s an example of Kotlin code that creates a simple “Hello, World!” app in Android:

class MainActivity : AppCompatActivity() {
    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(R.layout.activity_main)
        val textView = findViewById<TextView>(R.id.text_view)
        textView.text = "Hello, World!"
    }
}

Server-side web development: Kotlin can be used to create server-side web applications using frameworks like Ktor or Spring Boot. Here’s an example of Kotlin code that creates a simple web server using Ktor:

import io.ktor.application.*
import io.ktor.response.*
import io.ktor.routing.*
import io.ktor.server.engine.*
import io.ktor.server.netty.*

fun main() {
    embeddedServer(Netty, port = 8080) {
        routing {
            get("/") {
                call.respondText("Hello, World!")
            }
        }
    }.start(wait = true)
}

Desktop app development: Kotlin can be used to create cross-platform desktop applications using frameworks like TornadoFX. Here’s an example of Kotlin code that creates a simple window with a label:

class HelloWorld : App() {
    override fun start(stage: Stage) {
        val label = Label("Hello, World!")
        val scene = Scene(label, 200.0, 100.0)
        stage.scene = scene
        stage.show()
    }
}

Command-line tools: Kotlin can be used to create command-line tools that run on a variety of platforms. Here’s an example of Kotlin code that creates a simple command-line tool that prints “Hello, World!” to the console:
```
fun main(args: Array<String>) {
    println("Hello, World!")
}
```

Mobile app development: Kotlin can also be used to develop iOS apps using the Kotlin Multiplatform Mobile (KMM) framework. Here’s an example of Kotlin code that creates a simple “Hello, World!” app in iOS:

import kotlinx.cinterop.*
import platform.UIKit.*

class ViewController : UIViewController() {
    override fun viewDidLoad() {
        super.viewDidLoad()
        val label = UILabel().apply {
            translatesAutoresizingMaskIntoConstraints = false
            text = "Hello, World!"
        }
        view.addSubview(label)
        label.centerXAnchor.constraintEqualToAnchor(view.centerXAnchor).isActive = true
        label.centerYAnchor.constraintEqualToAnchor(view.centerYAnchor).isActive = true
    }
}

These are just a few examples of the many use cases for Kotlin. With its modern syntax and powerful features, Kotlin is a versatile language that can be used to develop a wide range of applications.