code: public static List<File> sortDataDir(File[] files, String prefix, boolean ascending)
      {
          if(files==null)
              return new ArrayList<File>(0);
          List<File> filelist = Arrays.asList(files);
          Collections.sort(filelist, new DataDirFileComparator(prefix, ascending));
          return filelist;
      }
docs: Sort the list of files. Recency as determined by the version component
  of the file name.
  
  @param files array of files
  @param prefix files not matching this prefix are assumed to have a
  version = -1)
  @param ascending true sorted in ascending order, false results in
  descending order
  @return sorted input files