java向某url发送一条post请求，并输出返回值字符串

在Java中，你可以使用HttpURLConnection或者第三方库如Apache HttpClient或者OkHttp来发送POST请求并获取响应。这里我们以HttpURLConnection为例：

import java.io.BufferedReader;
import java.io.InputStreamReader;
import java.net.HttpURLConnection;
import java.net.URL;

public class PostRequestExample {
    private static final String POST_URL = "http://example.com/api/endpoint"; // 替换为你实际的URL

    public static void main(String[] args) throws Exception {
        URL url = new URL(POST_URL);
        HttpURLConnection connection = (HttpURLConnection) url.openConnection();
        connection.setRequestMethod("POST");
        
        // 设置POST参数，例如这里是JSON格式
        String postData = "{\"key\":\"value\"}";
        byte[] bytes = postData.getBytes("UTF-8");
        connection.setDoOutput(true);
        connection.getOutputStream().write(bytes);

        int responseCode = connection.getResponseCode();
        if (responseCode == HttpURLConnection.HTTP_OK) {
            BufferedReader in = new BufferedReader(new InputStreamReader(connection.getInputStream()));
            StringBuilder response = new StringBuilder();
            String inputLine;
            while ((inputLine = in.readLine()) != null) {
                response.append(inputLine);
            }
            in.close();
            
            // 输出响应字符串
            System.out.println("Response: " + response.toString());
        } else {
            System.out.println("Failed to send POST request. Response code: " + responseCode);
        }

        connection.disconnect();
    }
}

这段代码首先创建一个URL对象，然后通过HttpURLConnection对象连接到该URL并发起POST请求。如果HTTP状态码为200（成功），它将读取并打印出响应的内容。