retry on 50x errors (i'm new to java and sparkpost client) about java-sparkpost HOT 4 CLOSED

IRestConnection connection = new RestConnection(this.client, getEndPoint());
ResourceTransmissions.create(connection, 0, transmission);

catch (SparkPostErrorServerResponseException spex) {

	boolean handled = false;

	// further classify error message if possible
	try {
		Pattern p = Pattern.compile("[^\\{]*(\\{.*\\})[^\\}]*");
		Matcher m = p.matcher(spex.getMessage());

		if (m.find(0)) {
			String json = m.group(1);
			JsonParser jsonParser = new JsonParser();
			JsonObject jo = (JsonObject) jsonParser.parse(json);

			// check if the JSON response is "Suppression"
			if (jo.getAsJsonArray("errors").get(0).getAsJsonObject().get("code").getAsString().equals("1902")) {
				EmailDAO.markAsUnsubscribed(conn, em);

				Logger.log("Email not sent because user unsubscribed " + em.id);

				handled = true;

			} else if (500 <= spex.getResponseCode() && spex.getResponseCode() < 510){
				Logger.log("Sparkpost " + spex.getResponseCode() + " errors, skipping for now: " + em.id);

				handled = true;
			}
		}
	} catch (Exception ex) {
		Logger.error("Unable to determine SparkPost error: " + em.id, ex);
	}

	if (!handled) {
		Logger.error("SparkPost unknown error processing email: " + em.id, spex);
		// mark email as error first
		try {
			EmailDAO.markAsError(conn, em);
		} catch (SQLException ex) {
			Logger.error("Error marking email as error: " + em.id, ex);
		}
	}

private void forceFiveHundredError(int retries) throws SparkPostException, IOException {
        this.client = this.newConfiguredClient();
        IRestConnection connection = new RestConnection(this.client, "https://api.sparkpost.com/api/v1");

        try {
            // Do something to foce and internal server error
            ResourceSendingDomains.list(connection);

            throw new IllegalStateException("Error: Expected an exception");
        } catch (SparkPostException e) {
            if (e.getServerErrorResponses() != null) {
                System.out.println("Got response from server.");
                if (e.getServerErrorResponses().getResponseCode() >= 500 && e.getServerErrorResponses().getResponseCode() <= 599) {
                    System.out.println("Got a 5xx level error");
                    try {
                        // wait before retrying
                        Thread.sleep(retries * 10000);
                    } catch (InterruptedException e1) {

                    }
                    forceFiveHundredError(retries + 1);

                }
            } else {
                System.out.println("This is some other unexpected error!!!");
            }
        }
    }