private static File createSampleFile() {
		try {
			File file = File.createTempFile("java-sdk-", ".txt");
			file.deleteOnExit();

			Writer writer = new OutputStreamWriter(new FileOutputStream(file));
			writer.write("01234567890123456789\n");
			writer.write("01234567890123456789\n");
			writer.write("01234567890123456789\n");
			writer.write("01234567890123456789\n");
			writer.write("01234567890123456789\n");
			writer.close();

			return file;
		} catch (IOException e) {
			log.error("tmp file create failed.");
			return null;
		}
	}