Hello, Kotlin

Kotlin is a modern, statically-typed language created by JetBrains that runs on the JVM, meaning it compiles to the same bytecode as Java and can call Java code (and be called from it) directly. It's Google's officially preferred language for Android development, but it also runs as backend code, compiles to JavaScript, and even to native binaries.

Your first program

fun main() {
    println("Hello, Kodstigen!")
}

Compare this to Java's Hello example, and the difference is immediate:

• No wrapping class is required, fun main() is a genuine top-level function, Kotlin doesn't force everything to live inside a class.
• println(...) instead of System.out.println(...), far less ceremony for something you'll type constantly.
• No semicolons required at the end of lines (though they're legal if you want them).

Compiling and running

kotlinc hello.kt -include-runtime -d hello.jar
java -jar hello.jar

kotlinc is the Kotlin compiler, -include-runtime bundles the small Kotlin standard library into the jar so it runs anywhere a JVM exists, without a separate Kotlin install.