code: public static String flatten(String left, String right) {
  		return left == null || left.isEmpty() ? right : left + "." + right;
  	}
docs: Links the two field names into a single left.right field name.
  If the left field is empty, right is returned
  
  @param left one field name
  @param right the other field name
  
  @return left.right or right if left is an empty string