The point of using bit masking to combine 4 nibbles into an int is to *avoid* object creation. Adding more object creation seems counterproductive.

Please remove the constructor. This should be a static helper class only. I do agree with removing the ... extends NibbleQuadHashed though. They should really be using static imports, not abusing extends.

I think this is the only major issue left before I can accept the changes. Everything else looks okay now.