/* 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() }