メモ
scala> import java.net._
import java.net._
scala> InetAddress.getByName("127.0.0.1") match { case _:Inet6Address => 2 case _:Inet4Address => 1 case _ => 0 }
res0: Int = 1
scala> InetAddress.getByName("::1") match { case _:Inet6Address => 2 case _:Inet4Address => 1 case _ => 0 }
res1: Int = 2