static void init() throws IOException {
		File downloadedUrlRecord = new File("gutenberg/url2.txt");
		if (!downloadedUrlRecord.exists()) {
			downloadedUrlRecord.createNewFile();
		}
		downloadedUrls = new HashSet<String>();
		BufferedReader br = new BufferedReader(new FileReader(
				downloadedUrlRecord));
		String line = null;
		while ((line = br.readLine()) != null) {
			downloadedUrls.add(line);
		}
		br.close();
		downloadedUrlWriter = new BufferedWriter(new FileWriter(
				downloadedUrlRecord));

		failedUrls = new HashSet<String>();
		File failedUrlRecord = new File("gutenberg/failurl2.txt");
		if (!failedUrlRecord.exists()) {
			failedUrlRecord.createNewFile();
		}
		failedUrlWriter = new BufferedWriter(new FileWriter(failedUrlRecord));
	}