df-convert.scala

def camelToUnderscores(name: String) = "[A-Z\\d]".r.replaceAllIn(name, {m =>
    "_" + m.group(0).toLowerCase()
})

def underscoresToCamel(name: String) = {
  val splitted = name.split("_")
  val converted = splitted.head.toLowerCase() +: splitted.tail.map(_.capitalize)
  converted.mkString
}

val columnsLower = df.columns.map(x => col(x).as(x.toLowerCase))
val columnsCamel = df.columns.map(x => col(x).as(underscoresToCamel(x)))
val dfLower = df.select(columnsLower: _*)
val dfCamel = df.select(columnsCamel: _*)