HTTP POST

public class httpPost {

    private String response = null;
    private String URL      = "https://mio url";

    public String invio() {

        StrictMode.ThreadPolicy policy = new StrictMode.ThreadPolicy.Builder().permitAll().build();
        StrictMode.setThreadPolicy(policy);

        try {
            URL url = new URL(URL);

            HttpURLConnection conn = (HttpURLConnection) url.openConnection();
            conn.setRequestMethod("POST");
            conn.setDoInput(true);
            conn.setDoOutput(true);

            Uri.Builder builder = new Uri.Builder();

        //Parametri da passare
            builder.appendQueryParameter("chiave1", "valore1");
            builder.appendQueryParameter("chiave2", "valore2");
            builder.appendQueryParameter("chiave3", "valore3");
            builder.appendQueryParameter("chiave4", "valore4");

            String query = builder.build().getEncodedQuery();

            OutputStream os = conn.getOutputStream();
            BufferedWriter writer = new BufferedWriter(
                    new OutputStreamWriter(os, StandardCharsets.UTF_8));
            writer.write(query);
            writer.flush();
            writer.close();

            InputStream in = new BufferedInputStream(conn.getInputStream());
            response = http.InputStreamToString(in);

        } catch (MalformedURLException e) {
            Log.e("HTTP", "MalformedURLException: " + e.getMessage());
        } catch (ProtocolException e) {
            Log.e("HTTP", "ProtocolException: " + e.getMessage());
        } catch (IOException e) {
            Log.e("HTTP", "IOException: " + e.getMessage());
        } catch (Exception e) {
            Log.e("HTTP", "Exception: " + e.getMessage());
        }

        return response;
    }
}