Classes

Although Kotlin is a multi-paradigm language, it has a strong affinity to the Java programming language, which is based on classes. Keeping Java and JVM interoperability in mind, it’s no wonder that Kotlin also has the notion of classes.

A class is a collection of data, called properties, and methods. To declare a class, we use the class keyword, exactly like Java. Let’s imagine we’re building a video game. We can define a class to represent the player as follows:

class Player {
}

The instantiation of a class simply looks like this:

val player = Player()

Notice that there’s no new keyword in Kotlin. The Kotlin compiler knows that we want to create a new instance of that class by the round brackets after the class name.

If the class has no body, as in this simple example, we can omit the curly braces:

class Player // Totally fine

Primary constructor

It would be useful for the player to be able to specify their name during creation. In ...