code: public File createDir(File dir) throws DataUtilException {
          if(dir == null) {
              throw new DataUtilException("Dir parameter can not be a null value");
          }
          if(dir.exists()) {
              throw new DataUtilException("Directory already exists: " + dir.getAbsolutePath());
          }
          if(! dir.mkdir()) {
              throw new DataUtilException("The result of File.mkDir() was false. Failed to create directory. : "
                      + dir.getAbsolutePath());
          }
          trackedFiles.add(dir);
          return dir;
      }
docs: Create and add a new directory
  @param dir new directory
  @return file new directory