Token request

    private final static String authserver = "https://authserver.mojang.com";

    public static void main(String[] args) throws Exception
    {
        System.out.println(authenticate("emilien.*******@*******.net", "e**********0"));
        System.out.println(authenticate("e**********@gmail.com", "s***********8"));
    }

    public static String authenticate(String username, String password) throws Exception {

        String genClientToken = UUID.randomUUID().toString();

        // Setting up json POST request
        String payload = "{\"agent\": {\"name\": \"Minecraft\",\"version\": 1},\"username\": \"" + username
                + "\",\"password\": \"" + password + "\",\"clientToken\": \"" + genClientToken + "\"}";

        String output = postReadURL(payload, new URL(authserver + "/authenticate"));

        // Setting up patterns
        String authBeg = "{\"accessToken\":\"";
        String authEnd = "\",\"clientToken\":\"";

        // What we are looking for
        String authtoken = getStringBetween(output, authBeg, authEnd);
        return authtoken;
    }


    private static String postReadURL(String payload, URL url) throws Exception {
        HttpURLConnection con = (HttpURLConnection) (url.openConnection());

        con.setReadTimeout(15000);
        con.setConnectTimeout(15000);
        con.setRequestMethod("POST");
        con.setRequestProperty("Content-Type", "application/json");
        con.setDoInput(true);
        con.setDoOutput(true);

        OutputStream out = con.getOutputStream();
        out.write(payload.getBytes("UTF-8"));
        out.close();

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

        String output = "";
        String line = null;
        while ((line = in.readLine()) != null)
            output += line;

        in.close();

        return output;
    }

    private static String getStringBetween(String base, String begin, String end) {

        Pattern patbeg = Pattern.compile(Pattern.quote(begin));
        Pattern patend = Pattern.compile(Pattern.quote(end));

        int resbeg = 0;
        int resend = base.length() - 1;

        Matcher matbeg = patbeg.matcher(base);

        if (matbeg.find())
            resbeg = matbeg.end();

        Matcher matend = patend.matcher(base);

        if (matend.find())
            resend = matend.start();

        return base.substring(resbeg, resend);
    }