当返回代码401时，Java HttpURLConnection自动附加身份验证头。

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.net.HttpURLConnection;
import java.net.URL;

public class HttpURLConnectionExample {
    public static void main(String[] args) throws IOException {
        String url = "http://example.com/api/resource";
        String username = "your-username";
        String password = "your-password";

        URL apiUrl = new URL(url);
        HttpURLConnection connection = (HttpURLConnection) apiUrl.openConnection();

        // 设置身份验证信息
        String authString = username + ":" + password;
        String authHeaderValue = "Basic " + java.util.Base64.getEncoder().encodeToString(authString.getBytes());
        connection.setRequestProperty("Authorization", authHeaderValue);

        // 发送请求
        int responseCode = connection.getResponseCode();

        if (responseCode == HttpURLConnection.HTTP_UNAUTHORIZED) {
            // 处理身份验证失败的情况
            System.out.println("身份验证失败");
        } else {
            // 处理其他响应
            BufferedReader reader = new BufferedReader(new InputStreamReader(connection.getInputStream()));
            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());
        }

        connection.disconnect();
    }
}