public static boolean isOk(URL url) {
		try {
			HttpURLConnection httpURLConnection = (HttpURLConnection) url.openConnection();
			httpURLConnection.setRequestMethod("HEAD");
			httpURLConnection.connect();
			boolean ret = httpURLConnection.getResponseCode() == HttpURLConnection.HTTP_OK;
			httpURLConnection.disconnect();
			return ret;
		} catch (IOException e) {
			e.printStackTrace();
		}
		return false;
	}