Interfaces in Kotlin

interface Speaker {
    fun speak()
}
class Dog : Speaker {
    override fun speak() {
        println("Woof")
    }
}

Full lesson:

An interface defines what a class can do, not how it does it or what it is. A Truck, a Robot, and a Drone aren't the same kind of thing — but they can all move(). You'd put move() in a Movable interface and have each one implement it.

Interface vs abstract class

A class inherits from at most one parent class but can implement many interfaces. That's why interfaces are the right tool for cross-cutting capabilities like Comparable, Serializable, Iterable, etc.

The language landscape

• Kotlin — first-class interface keyword. A class lists the interfaces it implements after :, and each implemented function is marked override.
• C# / Java — first-class interface keyword. C# uses : for both inheritance and implementation; Java uses extends for inheritance and implements for interfaces.
• Python — no separate interface; abstract base classes (ABCs) with all-abstract methods serve the same role.
• JavaScript — no interface keyword in plain JS (TypeScript has it). The convention is a stub class.
• C++ — a class with only pure-virtual methods is an interface. Multiple inheritance lets a class implement several.

Your task

The Speaker interface is already declared. Create a Dog class that implements it, with a speak() method that prints "Woof".

Expected output:

Woof