A modern programming language that makes developers happier.

Why Kotlin?

• Concise

  Drastically reduce the amount of boilerplate code

  /*
   Create a POJO with getters, setters, `equals()`, `hashCode()`, `toString()` and `copy()` in a 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"
  }
  

• Safe

  Avoid entire classes of errors such as null pointer exceptions

  /*
   Get rid of those pesky NullPointerExceptions, you know, The Billion Dollar Mistake
  */
  
  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()
  }
  

• Interoperable

  Leverage existing libraries for the JVM, Android, and the browser

  /*
   Use any existing library on the JVM, as there’s 100% compatibility, including SAM support.
  */
  
  import io.reactivex.Flowable
  import io.reactivex.schedulers.Schedulers
  
  Flowable
      .fromCallable {
          Thread.sleep(1000) //  imitate expensive computation
          "Done"
      }
      .subscribeOn(Schedulers.io())
      .observeOn(Schedulers.single())
      .subscribe(::println, Throwable::printStackTrace)
  

  // 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!"
  }
  

• Tool-friendly

  Choose any Java IDE or build from the command line

  • IntelliJ IDEA

    Bundled with both IntelliJ IDEA Community Edition and IntelliJ IDEA Ultimate

    Download Instructions

  • Android Studio

    Bundled with Android Studio

    Download Instructions

  • Eclipse

    Install the plugin from the Eclipse Marketplace

    Instructions

  • Standalone Compiler

    Use any editor and build from the command line

    Instructions