Practical Scala; Walking a tree directory

One of my requirements for botlist is to have a searchable help system. E.g. instead of man pages or Java API. I want to be able to add files to a directory. Index the files in the directory and then have the data as searchable. All of this through a command line interface. I started some initial code and used the following Scala idioms:

First Version, use of File Class:

class DocWalkFile(file: File) { 
def children = new Iterable[File] {
   def elements =
     if (file.isDirectory) file.listFiles.elements else Iterator.empty;
}
def andTree : Iterable[File] = (
     Seq.single(file) ++ children.flatMap(child => new DocWalkFile(child).andTree))
 }
 def listDocuments(dir: File): List[File] =
(new DocWalkFile(dir)).andTree.toList filter (f => (f.getName.endsWith(".java") || f.getName.endsWith(".txt")))
 

Second Version:

import java.io.File

object DocWalkFile {
  def andTree(dir: File): List[File] = {
    val fileList = dir.listFiles.toList
    (fileList filter(f => f.isFile && f.getName.endsWith(".txt"))) :::
       (fileList filter(f => f.isDirectory) flatMap (f => andTree(f) ))
  }
  def main(args: Array[String]): Unit = {
    if (args length == 0)
      println("usage: DocWalkFile [dir]")
    else {
      println("using dir " + args.apply(0));
      andTree(new
         File(args.apply(0))).foreach(f => println(">> " + f))
    }
  }

}

Resources:

• http://www.rosettacode.org/rosettacode/w/index.php?title=Walk_Directory_Tree