Hands-On Design Patterns with Kotlin

Inheritance

Exactly like in Java, abstract classes are marked by abstract and interfaces by the interface keyword:

abstract class AbstractDungeonMaster {    abstract val gameName: String    fun startGame() {        println("Game $gameName has started!")    }}interface Dragon

As in Java 8, interfaces in Kotlin can have a default implementation of functions, as long as they don't rely on any state:

interface Greeter {    fun sayHello() {        println("Hello")    }}

There are no inherits and implements keywords in Kotlin. Instead, both the name of an abstract class and all the names of the interfaces that class implements are put after a colon:

class DungeonMaster: Greeter, AbstractDungeonMaster() {    override val gameName: String        get() = "Dungeon of the Beholder"}

We ...