使用HttpUtli工具访问get请求并且设置请求头

好的，我可以回答您的问题。使用HttpUtil工具访问get请求，并设置请求头的代码如下：

import java.net.HttpURLConnection;
import java.net.URL;
import java.util.HashMap;
import java.util.Map;

public class HttpUtil {

    public static String sendGetRequest(String url, Map<String, String> headers) {
        String result = "";
        try {
            URL connection = new URL(url);
            HttpURLConnection httpURLConnection = (HttpURLConnection) connection.openConnection();
            httpURLConnection.setRequestMethod("GET");
            if (headers != null && headers.size() != 0) {
                for (Map.Entry<String, String> entry : headers.entrySet()) {
                    httpURLConnection.setRequestProperty(entry.getKey(), entry.getValue());
                }
            }

            httpURLConnection.setConnectTimeout(5000);
            httpURLConnection.setReadTimeout(5000);

            int responseCode = httpURLConnection.getResponseCode();
            if (responseCode == 200) {
                result = readStream(httpURLConnection.getInputStream());
            }
        } catch (Exception e) {
            e.printStackTrace();
        }
        return result;
    }

    private static String readStream(InputStream in) {
        BufferedReader reader = null;
        StringBuffer response = new StringBuffer();
        try {
            reader = new BufferedReader(new InputStreamReader(in));
            String line;
            while ((line = reader.readLine()) != null) {
                response.append(line);
            }
            reader.close();
        } catch (Exception e) {
            e.printStackTrace();
        } finally {
            if (reader != null) {
                try {
                    reader.close();
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
        }
        return response.toString();
    }

    public static void main(String[] args) {
        String url = "http://www.example.com";
        Map<String, String> headers = new HashMap<>();
        headers.put("User-Agent", "Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/58.0.3029.110 Safari/537.3");
        String response = sendGetRequest(url, headers);
        System.out.println(response);
    }
}

您可以将上述代码复制到您的Java项目中，并按照自己的需求进行修改。记得引入必要的Java IO包和Java网络包。