private static HttpURLConnection connection;
  
public static void main(String[] args) {
    BufferedReader reader;
  String line;
  StringBuffer responseContent = new StringBuffer();
  
  StringBuilder response = null;
 try {
        URL url = new URL("https://gateway.zibal.ir/v1/request");
  connection = (HttpURLConnection) url.openConnection();
  // Request setup
  connection.setRequestMethod("POST");
  connection.setRequestProperty("Content-Type", "application/json; utf-8");
  connection.setRequestProperty("Accept", "application/json");
  connection.setDoOutput(true);
  String jsonInputString = "{" +
                "\"merchant\": \"zibal\",\n" +
                "\"amount\": 160000,\n" +
                "\"callbackUrl\": \"http://yourapiurl.com/callback.php\"" +
                "}";
 try (OutputStream os = connection.getOutputStream()) {
            byte[] input = jsonInputString.getBytes("utf-8");
  os.write(input, 0, input.length);
  }
        try (BufferedReader br = new BufferedReader(
                new InputStreamReader(connection.getInputStream(), "utf-8"))) {
            response = new StringBuilder();
  String responseLine = null;
 while ((responseLine = br.readLine()) != null) {
                response.append(responseLine.trim());
  }
        }
        int status = connection.getResponseCode();
  System.out.println(status);
  
  
  } catch (MalformedURLException e) {
        e.printStackTrace();
  } catch (IOException e) {
        e.printStackTrace();
  }
  
    // Parse response JSON into JSONObject
  JSONObject result = new JSONObject(response.toString());
  System.out.println(result.getString("message"));
  
}