I keep getting this IOException error message "Can't reset method: already connected", on my spring boot program

Question

@GetMapping("/check")
    public String checkURL(@RequestParam String url) {
        String returnMessage = "";

        try {
            URL urlObj = new URL(url);
            HttpURLConnection conn = (HttpURLConnection) urlObj.openConnection();

            conn.connect();
            conn.setRequestMethod("GET");
            
            
            int responseCode = conn.getResponseCode() / 100;

            conn.disconnect();

            if (responseCode != 4 || responseCode != 3) {
                returnMessage = siteStatus + " UP AND RUNNING";
            } else {
                returnMessage = siteStatus + " DOWN!";
            }

        } catch (MalformedURLException e) {

            return siteStatus + " incorrect. Please try again.";
        } catch (IOException e) {
                        returnMessage = e.getMessage();
        }
        return returnMessage;
    }

This error is clearly due to IOException, if someone could help me fix this problem. I checked the URL is valid. I go to localhost:8080/check?url=https://www.example.com. I am pretty sure the syntax is correct. I even do conn.disconnect() to drop the connection yet I keep getting the error.