public static void deleteFile(String filename) throws IOException {
		File file = new File(filename);
		log.trace("Delete file = " + filename);
		if (file.isDirectory()) {
			throw new IOException("IOException -> BadInputException: not a file.");
		}
		if (file.exists() == false) {
			throw new IOException("IOException -> BadInputException: file is not exist.");
		}
		if (file.delete() == false) {
			throw new IOException("Cannot delete file. filename = " + filename);
		}
	}