帮我使用java写一个http的工具类

好的，以下是一个使用Java编写的HTTP工具类的示例，你可以根据自己的需求进行修改和完善：

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

public class HttpUtil {
    private String url;

    public HttpUtil(String url) {
        this.url = url;
    }

    public String get(Map<String, String> params, Map<String, String> headers) {
        try {
            String paramStr = generateParamString(params);
            URL urlObj = new URL(this.url + paramStr);
            HttpURLConnection connection = (HttpURLConnection) urlObj.openConnection();
            connection.setRequestMethod("GET");
            setHeaders(connection, headers);
            BufferedReader in = new BufferedReader(new InputStreamReader(connection.getInputStream()));
            String inputLine;
            StringBuilder response = new StringBuilder();
            while ((inputLine = in.readLine()) != null) {
                response.append(inputLine);
            }
            in.close();
            connection.disconnect();
            return response.toString();
        } catch (IOException e) {
            e.printStackTrace();
            return null;
        }
    }

    public String post(String data, Map<String, String> headers) {
        try {
            URL urlObj = new URL(this.url);
            HttpURLConnection connection = (HttpURLConnection) urlObj.openConnection();
            connection.setRequestMethod("POST");
            setHeaders(connection, headers);
            connection.setDoOutput(true);
            connection.getOutputStream().write(data.getBytes());
            BufferedReader in = new BufferedReader(new InputStreamReader(connection.getInputStream()));
            String inputLine;
            StringBuilder response = new StringBuilder();
            while ((inputLine = in.readLine()) != null) {
                response.append(inputLine);
            }
            in.close();
            connection.disconnect();
            return response.toString();
        } catch (IOException e) {
            e.printStackTrace();
            return null;
        }
    }

    private void setHeaders(HttpURLConnection connection, Map<String, String> headers) {
        if (headers != null) {
            for (Map.Entry<String, String> entry : headers.entrySet()) {
                connection.setRequestProperty(entry.getKey(), entry.getValue());
            }
        }
    }

    private String generateParamString(Map<String, String> params) {
        if (params == null) {
            return "";
        }
        StringBuilder sb = new StringBuilder();
        sb.append("?");
        for (Map.Entry<String, String> entry : params.entrySet()) {
            sb.append(entry.getKey());
            sb.append("=");
            sb.append(entry.getValue());
            sb.append("&");
        }
        return sb.toString();
    }
}

这个类中包含了两个常用的HTTP请求方法：GET和POST，分别使用HttpURLConnection发送HTTP请求。其中，GET方法接受两个可选参数params和headers，用于指定请求参数和请求头。POST方法接受两个可选参数data和headers，用于指定POST请求参数和请求头。如果请求发生错误，则返回null。