How to get first or last item from cqengine IndexedCollection with NavigableIndex

Pavel Niedoba :

I have com.googlecode.cqengine.IndexedCollection object with NavigableIndex configured. I need to get first or last item from the index or iterator of the index in general.

I suppose this should be trivial. I know I can create Query object with queryOptions object, use it to retrieve iterator from IndexedCollection and get first object, but I'm not sure if it's optimal for performance. Surely it's not elegant.

Pavel Niedoba :

With help of miradham I figured out that I need to remember indexes, since it's hard to pick up the right one if we have more of them. It will only work with NavigableIndex, we can't iterate base class Index

collection = new ConcurrentIndexedCollection<Data>();
index = NavigableIndex.onAttribute(Data.UNIQUE_TIMESTAMP);
collection.addIndex(index);

when I have the index:

try (CloseableIterator<KeyValue<String, Data>> iterator = indexUniqueTimestamp.getKeysAndValuesDescending(null).iterator()) {
        if (iterator.hasNext())
            return iterator.next().getValue();
    }
    return null;