Optimize GroupFacetCollector.getFacetEntries()

[gaobinlong]

Description

The method GroupFacetCollector.getFacetEntries() can be optimized by:

1. Initial ArrayList with known size.
2. Return empty ArrayList if offset >= total size.
3. Remove unnecessary local variable included, use entries.size() instead.

[dweiss]

In all honesty, I think the previous version was easier to understand and the gain is probably minimal (if at all detectable)?

[gaobinlong]

Thanks @dweiss , I reverted some change but kept the change of initial ArrayList with known size and return empty ArrayList if offset >= total size, are these also not necessary?