code: public static void touch(Resource res) throws IOException {
  	if (res.exists()) {
  	    res.setLastModified(System.currentTimeMillis());
  	}
  	else {
  	    res.createFile(true);
  	}
      }
docs: similar to linux bash function touch, create file if not exist otherwise change last modified
  date
  
  @param res
  @throws IOException