code: public static void cleanDirectory(File directory) throws IOException {
  		checkNotNull(directory, "directory");
  
  		guardIfWindows(FileUtils::cleanDirectoryInternal, directory);
  	}
docs: Removes all files contained within a directory, without removing the directory itself.
  
  <p>This method is safe against other concurrent deletion attempts.
  
  @param directory The directory to remove all files from.
  
  @throws FileNotFoundException Thrown if the directory itself does not exist.
  @throws IOException Thrown if the file indicates a proper file and not a directory, or if
  the directory could not be cleaned for some reason, for example
  due to missing access/write permissions.