public boolean accept(File pathname) {
    if (pathname.isDirectory())
      return recurse;
    String name = pathname.getName();
    if (! name.endsWith(extension))
      return false;
    int lastNumberIndex = getLastNumberIndex(name);
    if (lastNumberIndex == -1)
      return false;
    int numEndLoc = lastNumberIndex+1;
    int numStartLoc = getLastNonNumberIndex(name, lastNumberIndex)+1;
    int fileNum = Integer.parseInt(name.substring(numStartLoc, numEndLoc));
    if (fileNum >= lowFileNum && fileNum <= highFileNum)
      return true;
    return false;
  }