code: protected static File[] listDirs(File parent)
      {
          return parent.listFiles(new FileFilter()
          {
              public boolean accept(File file)
              {
                  return file.isDirectory();
              }
          });
      }
docs: List all of the sub-directories in a parent directory.
  
  @param parent Parent directory to search.
  
  @return All sub-directories under {@code parent}.