[Scala] sequence head 잘 뽑는 방법 | head of empty list 에러

Scala best practices에 따르면 sequence(list, map 등) 으로부터 head를 뽑을 때 `head` 보다는 `headOption` 사용을 권장

Seq.empty[Int].head
-> head of empty list exception 발생

headOption은 sequence의 head를 뽑아내는 좀 더 안전한 방법!
Seq(1, 2, 3).headOption
// res0: Option[Int] = Some(1)

Seq.empty[Int].headOption
// res1: Option[Int] = None

exception 방지를 위해서는 None이 아닌 조건을 넣으면 될듯