> Fortunately, there are several open-source libraries, that offer storing keys and values which allow storing keys and values as primitive values, without boxi

> Fortunately, there are several open-source libraries, that offer storing keys and values which allow storing keys and values as primitive values, without boxing: fastutil, agrona, koloboke. > In production, we use fastutil, because, based on our internal benchmarks, it shows better performance for read and write operations. I wonder how they arrived at this shortlist to test. I'd only heard of fastutil along with many not on this list (Trove, HPPC, CERN Colt, FastUtil, Joda Primitives, Eclipse Collections). Maybe agrona and koloboke are newer. The next time I need something similar I'll check them out.