REST Application - I don't receive the error from server in case of insucess - the output displays only if the request is successfull - rest

Question

I have the next problem: I've made a simple application which retrieves information from a server (GET Method). The application works fine as long as the information is retrieved successfully.
In case of insuccess, I don't receive the error from the server (ex: 401 - Unauthorized, 403 - Forbidden - when the authentication token is incorrect for example).
How can I fix this so that my application will return the error from server ? I've done also a POST method and there it's working, I received all erorrs froem server in case of insuccess.
What i'm doing wrong with this code ? Why i don't receive an error in case of insuccess?
The only error I receive in output is 400 in all scenarios and this isn't enough.
For example, if the authorization token is incorrect, I should receive from server 401 - Unauthorized. I know this because i'm doing test with other REST application (like POSTMAN). Can it be fixed to show the errors related to that scenarios ?
void example2() {
// GET METHOD !
try {
String webPage = "https://www.clients.ro";
String name = "user";
String password = "pass";
String authString = name + ":" + password;
System.out.println("Decoded authorization token" + authString);
//byte[] authEncBytes = Base64.encodeBase64(authString.getBytes());
//String authStringEnc = new String(authEncBytes);
byte[] authEncBytes = authString.getBytes(StandardCharsets.UTF_8);
String authStringEnc = DatatypeConverter.printBase64Binary(authEncBytes);
System.out.println("Token encoded in Base64 " + authStringEnc);
URL url = new URL(webPage);
URLConnection urlConnection = url.openConnection();
urlConnection.setRequestProperty("Authorization", "Basic " + authStringEnc);
InputStream is = urlConnection.getInputStream();
InputStreamReader isr = new InputStreamReader(is);
int numCharsRead;
char[] charArray = new char[1024];
StringBuffer sb = new StringBuffer();
while ((numCharsRead = isr.read(charArray)) > 0) {
sb.append(charArray, 0, numCharsRead);
}
String result = sb.toString();
System.out.println(result);
System.out.println();
} catch (MalformedURLException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
}
}