Kotlin Inheritance — open, override, and super

open class Animal(val name: String) {
    open fun sound(): String = "..."
    fun describe() = "$name says: ${sound()}"
}

class Dog(name: String) : Animal(name) {
    override fun sound() = "Woof"
}

class Cat(name: String) : Animal(name) {
    override fun sound() = "Meow"
}

fun main() {
    val animals = listOf(Dog("Rex"), Cat("Whiskers"), Dog("Buddy"))
    for (a in animals) println(a.describe())
}

abstract class Shape {
    abstract fun area(): Double
    fun describe() = "Area: ${"%.2f".format(area())}"
}

class Rectangle(val w: Double, val h: Double) : Shape() {
    override fun area() = w * h
}

class Circle(val r: Double) : Shape() {
    override fun area() = Math.PI * r * r
}

fun main() {
    val shapes: List<Shape> = listOf(Rectangle(4.0, 5.0), Circle(3.0))
    shapes.forEach { println(it.describe()) }
}

open class Vehicle(val brand: String) {
    open fun info() = "Brand: $brand"
}

class Car(brand: String, val model: String) : Vehicle(brand) {
    override fun info() = "${super.info()}, Model: $model"
}

fun main() {
    val car = Car("Toyota", "Corolla")
    println(car.info())
}