HttpClient是一個開源的Java HTTP客戶端庫，可以發送HTTP請求，并接收HTTP響應。

使用HttpClient發送GET請求的基本步驟如下：

1. 創建HttpClient對象：

CloseableHttpClient httpClient = HttpClients.createDefault();

2. 創建HttpGet對象，并設置請求的URL：

HttpGet httpGet = new HttpGet("http://www.example.com");

3. 執行GET請求并獲取響應：

CloseableHttpResponse response = httpClient.execute(httpGet);

4. 解析響應：

• 獲取響應狀態碼：

int statusCode = response.getStatusLine().getStatusCode();

• 獲取響應內容：

HttpEntity entity = response.getEntity();
String responseContent = EntityUtils.toString(entity, "UTF-8");

5. 關閉HttpClient和HttpResponse：

response.close();
httpClient.close();

完整的示例代碼如下：

import org.apache.http.HttpEntity;
import org.apache.http.client.methods.CloseableHttpResponse;
import org.apache.http.client.methods.HttpGet;
import org.apache.http.impl.client.CloseableHttpClient;
import org.apache.http.impl.client.HttpClients;
import org.apache.http.util.EntityUtils;
public class HttpClientDemo {
public static void main(String[] args) throws Exception {
CloseableHttpClient httpClient = HttpClients.createDefault();
HttpGet httpGet = new HttpGet("http://www.example.com");
CloseableHttpResponse response = httpClient.execute(httpGet);
try {
int statusCode = response.getStatusLine().getStatusCode();
HttpEntity entity = response.getEntity();
String responseContent = EntityUtils.toString(entity, "UTF-8");
System.out.println("Status Code: " + statusCode);
System.out.println("Response Content: " + responseContent);
} finally {
response.close();
}
httpClient.close();
}
}

以上代碼發送一個GET請求到http://www.example.com，并輸出響應狀態碼和響應內容。