//open 修饰的类才可以被继承
open class Product(val name: String) {
    fun description() = "Product:$name"

    //open 修饰的方法才可以重载
    open fun load() = "Nothing.."
}

class LuxuryProduct : Product("Luxury") {
    override fun load() = "Luxury"
}

fun main() {
    val p: Product = LuxuryProduct()
    println(p.load())
}