code: public Record []
  expand() throws IOException {
  	List list = new ArrayList();
  	for (long i = start; i < end; i += step) {
  		String namestr = substitute(namePattern, current);
  		Name name = Name.fromString(namestr, origin);
  		String rdata = substitute(rdataPattern, current);
  		list.add(Record.fromString(name, type, dclass, ttl,
  					   rdata, origin));
  	}
  	return (Record []) list.toArray(new Record[list.size()]);
  }
docs: Constructs and returns all records in the expansion.
  @throws IOException The name or rdata of a record was invalid after
  substitutions were performed.