Real World Example · Kotlin Introduction in Kotlin | Kotlin

Kotlin in Real Apps

Food delivery, payment and chat apps used daily in India — Zomato, Swiggy, PhonePe, Paytm, WhatsApp — run on Android, where Kotlin is now the main language for new code. Globally, Google (Maps, Drive, Play Store), Netflix, Uber, Pinterest and Trello use Kotlin, and many Spring Boot backends are written in Kotlin.

An Android Screen in Kotlin

This is what a simple Android screen looks like with Jetpack Compose (code only — it needs an Android device). You will learn every keyword in it during this course.

class MainActivity : ComponentActivity() {
    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContent {
            Text(text = "Hi Asha, your order is on the way!")
        }
    }
}

The Logic Behind It

Example

The screen only shows text. The logic that builds the text is plain Kotlin, which you can run anywhere:

fun main() {
    val customer = "Asha"
    val restaurant = "Paradise Biryani"
    val minutes = 25
    println("Hi $customer, your order from $restaurant is on the way!")
    println("Arriving in about $minutes minutes")
}

Output

Hi Asha, your order from Paradise Biryani is on the way!
Arriving in about 25 minutes

Exercise: Write a Kotlin program that prints your name on the first line and "I am learning Kotlin" on the second line.

Show answer

fun main() {
    println("Ravi")
    println("I am learning Kotlin")
}