you can specify the base to use when calling parseInt()
http://helpdesk.objects.com.au/java/how-to-parse-a-hex-stringSo parse it, add one, then convertit back to a base36 string
String s = Integer.toString(n, 32);
http://java.sun.com/javase/6/docs/api/java/lang/Integer.html#toString(int,%20int)