interface Animal {
    val id: String
    val sound: String
}

class AnimalBuilder {
    var id: String? = null
    var sound: String? = null

    fun withSound(sound: String): AnimalBuilder {
        this.sound = sound
        return this
    }

    fun withId(id: String): AnimalBuilder{
        this.id = id
        return this
    }

    fun build(): Animal {
        checkNotNull(id)
        checkNotNull(sound)
        val builder = this
        return object: Animal {
            override val id: String = builder.id!!
            override val sound: String = builder.sound!!
        }
    }
}

fun main() {
    val dog = AnimalBuilder()
        .withId("3.1415")
        .withSound("Bark")
        .build()
}