// time passes...
OperationResult<ColumnList<DateTime>> result = future.get();
ColumnList columns = result.getResult();
Iterator ii = columns.iterator();
while (ii.hasNext()) {
Column column = (Column) ii.next();
DateTime timestamp = (DateTime) column.getName();
Reading reading = new Reading(sensorId, timestamp, (Reading) column.getValue(ReadingSerializer.get()));
readings.add(reading);