static class MyAuthenticator extends Authenticator {
    public PasswordAuthentication getPasswordAuthentication() {
        System.out.println("trying to authenticate");
        return new PasswordAuthentication("user", "password".toCharArray());
    }
}

Authenticator.setDefault(new MyAuthenticator())

String encoding = Base64.encode("user:password".getBytes());
HttpURLConnection connection = (HttpURLConnection) url.openConnection();
connection.setRequestMethod("GET");
connection.setDoOutput(true);
connection.setRequestProperty  ("Authorization", "Basic " + encoding);