private static String getRefreshTokenFromFile() {
		String temp = null;
		JsonObject j;

		// checks if refresh token file exists
		File f = new File("refresh_token.json");
		if (!f.exists()) {
			return null;
		}

		// reads in refresh token file and parses out token value
		try {
			j = JsonObject.readFrom(openFile("refresh_token.json"));
			temp = j.get("refresh_token").asString();
		} catch (UnsupportedOperationException e) {
			return null;
		}

		return temp;
	}