如何使用HttpURLConnection for java android发送认证密钥？我收到错误代码500

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.net.HttpURLConnection;
import java.net.URL;
import java.nio.charset.StandardCharsets;
import java.util.Base64;

public class HttpURLConnectionExample {

    public static void main(String[] args) {
        String urlString = "http://example.com/api/endpoint";
        String username = "your_username";
        String password = "your_password";

        try {
            URL url = new URL(urlString);
            HttpURLConnection conn = (HttpURLConnection) url.openConnection();
            conn.setRequestMethod("POST");
            String credentials = username + ":" + password;
            String base64Credentials = Base64.getEncoder().encodeToString(credentials.getBytes(StandardCharsets.UTF_8));
            conn.setRequestProperty("Authorization", "Basic " + base64Credentials);

            // 设置其他请求头字段，如果需要的话

            int responseCode = conn.getResponseCode();
            if (responseCode == 500) {
                System.out.println("服务器发生错误");
                // 处理错误逻辑
            } else {
                InputStream inputStream = conn.getInputStream();
                BufferedReader reader = new BufferedReader(new InputStreamReader(inputStream));
                String line;
                StringBuilder response = new StringBuilder();
                while ((line = reader.readLine()) != null) {
                    response.append(line);
                }
                reader.close();
                System.out.println("响应内容: " + response.toString());
            }

            conn.disconnect();
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
}