code: private static String createTempDirectory(String baseDir, String fileStem) {
          Long nano = new Long(System.nanoTime());
          return baseDir + File.separator + fileStem + nano;
      }
docs: Generate unique directory name of form:
  basedir/fileStem<time-in-nanos>
  
  @param baseDir
  @param fileStem
  @return unique dir name