code: public static <T> void join(Collection<T> collection, String delimiter, StringBuilder sb, JoinCallback<T> join) {
  		boolean first = true;
  		for (T element : collection) {
  			if (!first) {
  				sb.append(delimiter);
  			}
  
  			join.handle(sb, element);
  			first = false;
  		}
  	}
docs: Joins a collection of values into a delimited list.
  @param collection the collection of values
  @param delimiter the delimiter (e.g. ",")
  @param sb the string builder to append onto
  @param join callback function to call on every element in the collection
  @param <T> the value class