A simaple example of return Option value:

def contact(input: List[String]): Option[String] = {
    if (input.isEmpty) {
        None
    } else {
        Some(input.reduce(_ + "|" + _))
    }
}
scala> def contact(input: List[String]): Option[String] = {
     |     if (input.isEmpty) {
     |         None
     |     } else {
     |         Some(input.reduce(_ + "|" + _))
     |     }
     | }
contact: (input: List[String])Option[String]

scala> val ss:List[String] = List("1","2","sss","44")
ss: List[String] = List(1, 2, sss, 44)

scala> contact(ss)
res6: Option[String] = Some(1|2|sss|44)

scala> val ss:List[String] = List()
ss: List[String] = List()

scala> contact(ss)
res8: Option[String] = None