Why Learn Kotlin language?

You can learn Kotlin language for following  reasons.

1. Safe

• Forget about NullPointerExceptions.

var output: String
output = null   // Compilation error

• Kotlin protects you from mistakenly operating on nullable types

val name: String? = null    // Nullable type
println(name.length())      // Compilation error

• And if you check a type is right, the compiler will auto-cast it for you

fun calculateTotal(obj: Any) {
    if (obj is Invoice)
        obj.calculateTotal()
}

2. Interoperable

• Use any existing java library on the JVM, as there’s 100% compatibility.
• Target either the JVM or JavaScript.
• Write code in Kotlin and decide where you want to deploy to

import kotlin.browser.window
fun onLoad() {
window.document.body!!.innerHTML += "<br/>Hello, Kotlin!"
}

3. Concise

• Implement code with easy and simple syntax and using few lines of code.
• Develop complex functionality using simple code.
• Create a POJO with getters, setters, equals(), hashcode(), toString() and copy() in single line:

data class Customer(val name: String, val email: String, val company: String)

• Or filter a list using a lambda expression:

val positiveNumbers = list.filter { it > 0 }

• Want a singleton? Create an object:

object ThisIsASingleton {
    val companyName: String = "JetBrains"
}

How To Get Started with Kotlin?

Assuming following prerequisite is installed on your computer.

1. IntelliJ IDEA
2. Java

Get started and follow below steps to create Kotlin project and run it on your computer.

• Open IntelliJ IDEA
• Click Create New Project

• On the left menu, select Kotlin > Kotlin (JVM) and hit Next

• Now, give this project a name: “HelloWorld” and select project location for this project and click finish.

• You should see your project on the left menu. If you can’t see this window, go to View > Tool Windows > Project
• Now create a new Kotlin file: Hello > New > Kotlin File/Class

• A pop up window will appear where you can provide name for the Kotlin file. We will name it main. Then, click OK.
• You can see the file main.kt
• kt is the file extension for Kotlin files.
• Now, write below code in this file and save it.

fun main(args : Array<String>) { 
  println("Hello, world!") 
}

• To run it, go to Run > Run

When you run the program, the output will be:

Hello, world!

How you can learn Kotlin?

You can learn Kotlin from tutorials available on this site. Checkout official site for more updates.

Kotlin reference and Kotlin tutorial from official site is the most reliable source to learn Kotlin. The official reference is continuously updated to keep up with changes to the Kotlin.

Build Applications For Platform

You can build applications for following platforms using Kotlin language.

1. JVM
2. Android
3. Browser
4. Native