for (final Iterator<AccumulatorRef> refIterator = _accumulators.iterator(); refIterator.hasNext();) {
final AccumulatorRef ref = refIterator.next();
if (!ref.isLive()) {
refIterator.remove();
}
final Accumulator acc = ref.takeCheckpointRef(timestamp);
if (acc != null) {
result.add(acc);
}
}
Collections.sort(result, Accumulator.SORT_COMPARATOR);