docs: public static boolean cleanEmpty(File directory) throws IORuntimeException {
  		if (directory == null || directory.exists() == false || false == directory.isDirectory()) {
  			return true;
  		}
  
  		final File[] files = directory.listFiles();
  		if(ArrayUtil.isEmpty(files)) {
  			//空文件夹则删除之
  			directory.delete();
  		}
  		for (File childFile : files) {
  			clean(childFile);
  		}
  		return true;
  	}