Scala - Regex on contents of several files

RegexOnSeveralFiles.scala

  /** my projects are named GuinePigModels, GuineaPigController, etc */
  private val myProjectsPrefix = "GuineaPig"

  /** jar names appear on lines which may end by a comma followed by a line continuation mark */
  private val jarRef = """^([A-Za-z0-9_.\-]+)(\.jar)(,\\)*""".r

  /** list files recursively */
  private def listOfFiles(dir: File): Seq[File] = {
    if (dir.exists && dir.isDirectory) {
      dir.listFiles.filter(f => f.isFile).toList
    } else {
      Seq.empty[File]
    }
  }

  /** filter jar names related to internal dependencies, i.e.: matching my project names */
  private def onlyInternalJars(name: String): Boolean =
    name.toLowerCase.startsWith(myProjectsPrefix)

  /** filter jar names related to external dependencies, i.e.: not matching my project names */
  private def onlyExternalJars(name: String): Boolean =
    !name.toLowerCase.startsWith(myProjectsPrefix)

  /** parse a single line of text and optionally returns one jar name from it */
  private def parse(line: String): Option[String] =
    line match {
      case jarRef(name, _*) => Some(name)
      case _ => None:Option[String]
    }

  /** parse a file and returns a Set of jar names from it */
  private def parse(f: File): Set[String] = {
    (for(
      line <- scala.io.Source.fromFile(f).getLines();
      result <- parse(line) if(result != null)
    ) yield {
      result
    }).toSet
  }

  /** parses several files from a directory and returns a Set of jar names from them */
  private def referencedJars(dir: File, jarFilter: (String) => Boolean): Set[String] =
    (Set.empty[String] /: listOfFiles(dir).map(f => parse(f))) {
      case (acc, item) =>
        acc ++ item.filter(jarFilter)
    }

  /** parses several files from a directory and returns a Set of internal jar names from them */
  def referencedInternalJars(dir: File): Set[String] =
    referencedJars(dir, onlyInternalJars)

  /** parses several files from a directory and returns a Set of external jar names from them */
  def referencedExternalJars(dir: File): Set[String] =
    referencedJars(dir, onlyExternalJars)