How Do I Configure the referer Header? (SDK for Java)

import com.obs.services.ObsClient;
import com.obs.services.exception.ObsException;
import com.obs.services.model.PutObjectRequest;
import java.io.File;
public class PutObject004 {
    public static void main(String[] args) {
        // Obtain an AK/SK pair using environment variables or import the AK/SK pair in other ways. Using hard coding may result in leakage.
        // Obtain an AK/SK pair on the management console.
        String ak = System.getenv("ACCESS_KEY_ID");
        String sk = System.getenv("SECRET_ACCESS_KEY_ID");
        // (Optional) If you are using a temporary AK/SK pair and a security token to access OBS, you are advised not to use hard coding, which may result in information leakage.
        // Obtain an AK/SK pair and a security token using environment variables or import them in other ways.
        // String securityToken = System.getenv("SECURITY_TOKEN");
        // Enter the endpoint corresponding to the bucket. EU-Dublin is used here as an example. Replace it with the one currently in use.
        String endPoint = "https://obs.eu-west-101.myhuaweicloud.eu"; 
        // Obtain an endpoint using environment variables or import it in other ways.
        //String endPoint = System.getenv("ENDPOINT");
        
        // Create an ObsClient instance.
        // Use a permanent AK/SK pair to initialize the client.
        ObsClient obsClient = new ObsClient(ak, sk,endPoint);
        // Use a temporary AK/SK pair and security token to initialize the client.
        // ObsClient obsClient = new ObsClient(ak, sk, securityToken, endPoint);

        try {
            // Upload a file.
            // localfile indicates the path of the local file to be uploaded, in which the file name must be specified.
            PutObjectRequest request = new PutObjectRequest();
            request.setBucketName("examplebucket");
            request.setObjectKey("objectkey");
            request.setFile(new File("localfile"));
            HashMap<String, String> userHeaders = new HashMap<>();
            // Specify the referer header when uploading an object.
            userHeaders.put("referer","https://example.com*");
            request.setUserHeaders(userHeaders);
            PutObjectResult putObjectResult = obsClient.putObject(request); 
            System.out.println("putObject successfully");
        } catch (ObsException e) {
            System.out.println("putObject failed");
            // Request failed. Print the HTTP status code.
            System.out.println("HTTP Code:" + e.getResponseCode());
            // Request failed. Print the server-side error code.
            System.out.println("Error Code:" + e.getErrorCode());
            // Request failed. Print the error details.
            System.out.println("Error Message:" + e.getErrorMessage());
            // Request failed. Print the request ID.
            System.out.println("Request ID:" + e.getErrorRequestId());
            System.out.println("Host ID:" + e.getErrorHostId());
            e.printStackTrace();
        } catch (Exception e) {
            System.out.println("putObject failed");
            // Print other error information.
            e.printStackTrace();
        }
    }
}