你是一名java程序员，请用apache http 封装一个HttpUtils工具类

好的，我可以为你编写一个简单的 `HttpUtils` 工具类，使用 Apache HttpClient 来进行 HTTP 请求的封装。以下是一个示例：

import org.apache.http.HttpEntity;
import org.apache.http.HttpResponse;
import org.apache.http.NameValuePair;
import org.apache.http.client.entity.UrlEncodedFormEntity;
import org.apache.http.client.methods.HttpGet;
import org.apache.http.client.methods.HttpPost;
import org.apache.http.client.utils.URIBuilder;
import org.apache.http.impl.client.CloseableHttpClient;
import org.apache.http.impl.client.HttpClientBuilder;
import org.apache.http.message.BasicNameValuePair;
import org.apache.http.util.EntityUtils;

import java.io.IOException;
import java.net.URI;
import java.net.URISyntaxException;
import java.util.ArrayList;
import java.util.List;

public class HttpUtils {

    private static final String DEFAULT_CHARSET = "UTF-8";

    public static String sendGetRequest(String url) throws IOException {
        CloseableHttpClient httpClient = HttpClientBuilder.create().build();
        HttpGet request = new HttpGet(url);
        HttpResponse response = httpClient.execute(request);
        return extractResponse(response);
    }

    public static String sendGetRequestWithParams(String url, List<NameValuePair> params) throws URISyntaxException, IOException {
        CloseableHttpClient httpClient = HttpClientBuilder.create().build();

        URIBuilder uriBuilder = new URIBuilder(url);
        uriBuilder.addParameters(params);

        URI uri = uriBuilder.build();
        HttpGet request = new HttpGet(uri);

        HttpResponse response = httpClient.execute(request);
        return extractResponse(response);
    }

    public static String sendPostRequest(String url, List<NameValuePair> params) throws IOException {
        CloseableHttpClient httpClient = HttpClientBuilder.create().build();
        HttpPost request = new HttpPost(url);

        UrlEncodedFormEntity entity = new UrlEncodedFormEntity(params, DEFAULT_CHARSET);
        request.setEntity(entity);

        HttpResponse response = httpClient.execute(request);
        return extractResponse(response);
    }

    private static String extractResponse(HttpResponse response) throws IOException {
        HttpEntity entity = response.getEntity();
        if (entity != null) {
            return EntityUtils.toString(entity, DEFAULT_CHARSET);
        } else {
            return null;
        }
    }

    // 示例用法
    public static void main(String[] args) {
        try {
            // 发送 GET 请求
            String getResponse = HttpUtils.sendGetRequest("https://www.example.com");
            System.out.println("GET 响应：" + getResponse);

            // 发送带参数的 GET 请求
            List<NameValuePair> params = new ArrayList<>();
            params.add(new BasicNameValuePair("param1", "value1"));
            params.add(new BasicNameValuePair("param2", "value2"));
            String getWithParamsResponse = HttpUtils.sendGetRequestWithParams("https://www.example.com", params);
            System.out.println("带参数的 GET 响应：" + getWithParamsResponse);

            // 发送 POST 请求
            List<NameValuePair> postParams = new ArrayList<>();
            postParams.add(new BasicNameValuePair("param1", "value1"));
            postParams.add(new BasicNameValuePair("param2", "value2"));
            String postResponse = HttpUtils.sendPostRequest("https://www.example.com", postParams);
            System.out.println("POST 响应：" + postResponse);
        } catch (IOException | URISyntaxException e) {
            e.printStackTrace();
        }
    }
}

在这个示例中，`HttpUtils` 类提供了三个静态方法来发送 GET 和 POST 请求，并返回响应结果。你可以根据需要添加其他方法和参数验证逻辑。请注意，示例中使用了默认的字符集编码为 UTF-8，你可以根据实际情况进行调整。