code: private static String uniquify(String id, Set<String> knownIds) {
  		int n = 10;
  		String olda = id;
  		while (knownIds.contains(id)) {
  			id = olda + Integer.toString(n, Character.MAX_RADIX);
  			++n;
  		}
  		return id;
  	}
docs: Makes the given ID unique
  @param id the ID
  @param knownIds a set of known IDs to compare to
  @return the unique IDs