无法将字符串作为HTTPContent发送

import java.io.UnsupportedEncodingException;
import java.net.HttpURLConnection;
import java.net.URL;
import java.net.URLEncoder;

public class HttpClient {
    public static void main(String[] args) throws Exception {
        String content = "要发送的字符串内容";
        String encodedContent = URLEncoder.encode(content, "UTF-8");

        // 构建HTTP连接
        URL url = new URL("http://example.com/api/endpoint");
        HttpURLConnection connection = (HttpURLConnection) url.openConnection();

        // 设置请求方法为POST
        connection.setRequestMethod("POST");

        // 设置Content-Type为application/x-www-form-urlencoded
        connection.setRequestProperty("Content-Type", "application/x-www-form-urlencoded");

        // 将编码后的字符串作为HTTPContent发送
        connection.setDoOutput(true);
        connection.getOutputStream().write(encodedContent.getBytes("UTF-8"));
        connection.getOutputStream().flush();
        connection.getOutputStream().close();

        // 处理响应结果
        int responseCode = connection.getResponseCode();
        if (responseCode == HttpURLConnection.HTTP_OK) {
            // 请求成功
            // ...
        } else {
            // 请求失败
            // ...
        }

        // 关闭连接
        connection.disconnect();
    }
}