Creating Instances of Classes

Java and Ruby both use new to create instances of classes, whether as a keyword in Java:

Foo foo = new Foo();

…or as a method in Ruby:

foo = Foo.new

JavaScript has a few flavors of creating objects, including one using the new keyword, much as you would in Java.

In Kotlin, though, you treat the class name as a function name, and just call it:

class Foo

fun main() {
  val foo = Foo()

  println(foo)
}

In effect, you are calling the class “constructor” this way — we will explore constructors more later in this chapter.

The println() call does not print much:

[object Object]

That is partly due to the limited built-in implementation of the toString() function that we inherit, and partly due to limitations in the Kotlin scripting environment used by Klassbook.