public static void writePhones(ConcurrentHashSet<Long> set, String file) throws IOException {
		if (file == null || file.equals(""))
			return;
		FileWriter fw = new FileWriter(new File(file));
		BufferedWriter bw = new BufferedWriter(fw);
		try {
			if (set.size() == 0) {
				bw.append("no phone numbers.");
				return;
			} else {
				Iterator<Long> iter = set.iterator();
				while (iter.hasNext()) {
					bw.append(iter.next() + "\n");
				}
			}
		} finally {
			bw.flush();
			bw.close();
		}

	}