final String URL = "http://www.sample.com/api/sendsms.php?username=name&password=pass&message=Your verification number is: "  + randomNum +
                            "&numbers=" + mobile + "&sender=app&return=json"

final String URL = "http://www.sample.com/api/sendsms.php?username=name&password=pass&message=Your%20verification%20number%20is:%20"  + randomNum +
                            "&numbers=" + mobile + "&sender=app&return=json";

String URL = "http://www.sample.com/api/sendsms.php?username=name&password=pass&message=Your verification number is: "  + randomNum +"&numbers=" + mobile + "&sender=app&return=json"
String newurl = URL.replaceAll(" ","%20");

final String URL = "http://www.sample.com/api/sendsms.php?username=name&password=pass&message=Your verification number is: "  + randomNum +"&numbers=" + mobile + "&sender=app&return=json"

  final String encodedURL = URLEncoder.encode(URL, "utf-8");