Java - Erro en conexión a url de internet mediante un proxy con autenticarión de usuario

package prueba;

import javax.net.ssl.HttpsURLConnection;

import java.io.BufferedReader;

import java.io.DataOutputStream;

import java.io.IOException;

import java.io.InputStreamReader;

import java.net.InetSocketAddress;

import java.net.Proxy;

import java.net.Proxy.Type;

import java.net.URL;

import java.util.Base64;

public class ConexionURL {

	public void verificarTokenRecaptcha(String urlVerificacion, String claveRecaptcha,

			String tokenRecaptcha) throws IOException {

		DataOutputStream wr=null;

		BufferedReader in=null;

		HttpsURLConnection con=null;

		String proxyHost="proxyempresa.com";

		int proxyPort=8080;

		System.setProperty("http.proxyHost", proxyHost);

		System.setProperty("http.proxyPort", "8080");

		String encoded = new String

		      (Base64.getEncoder().encode(new String("usuario:clave").getBytes()));

		try {

			//Proxy proxy=new Proxy(Type.HTTP, new InetSocketAddress(proxyHost, proxyPort));//Se intento usar tambien con esta linea pero el proxy usa autenticación con usuario

			URL obj = new URL(urlVerificacion);

			//con = (HttpsURLConnection) obj.openConnection(proxy);

			con = (HttpsURLConnection) obj.openConnection();

			con.setRequestProperty("Proxy-Authorization", "Basic " + encoded);

			con.connect();

			con.setRequestMethod("POST");

			String postParams = "secret=" + claveRecaptcha + "&response=" + tokenRecaptcha;

			con.setDoOutput(true);

			wr = new DataOutputStream(con.getOutputStream());

			wr.writeBytes(postParams);

			int responseCode = con.getResponseCode();

			in = new BufferedReader(new InputStreamReader(con.getInputStream()));

			String inputLine;

			StringBuffer response = new StringBuffer();

			while ((inputLine = in.readLine()) != null) {

				response.append(inputLine);

			}

			String jsonObject = response.toString();

			System.out.println("responseCode: " + responseCode);

			System.out.println("recaptchaSalida IsSuccess: " + jsonObject);

		} catch (Exception ex) {

			System.out.println("Error: "+ex.toString());

		} finally{

			if(wr!=null){

				wr.close();

			}

			if(in!=null){

				in.close();

			}

			if(con!=null){

				con.disconnect();

			}

		}

	}

}