String url = "http://maps.googleapis.com/maps/api/distancematrix/xml?origins="+origin+"&destinations="+destination+"&mode=driving&sensor=false&language=en-EN&units=imperial";
url = url.replaceAll(" ", "%20");

http://maps.googleapis.com/maps/api/distancematrix/xml?origins=150%20Sutter%20St%20San%20Francisco,%20CA,%20United%20States&destinations=1%20Palmer%20Sq%20E
Princeton,%20NJ%2008542&mode=driving&sensor=false&language=en-EN&units=imperial

java.net.MalformedURLException: Illegal character in URL

String url = "http://...";
String encodedUrl = null;

try {
    encodedUrl = URLEncoder.encode(url, "UTF-8");
} catch (UnsupportedEncodingException ignored) {
    // Can be safely ignored because UTF-8 is always supported
}

String url = "http://maps.googleapis.com/maps/api/distancematrix/xml?origins=" + URLEncoder.encode(origin, "UTF-8");