List, Set and Map implementations with a rich API. has additional types not found in the JDK like Bags, Multimaps. has set of utility classes that work with any JDK compatible collections, arrays, Maps or Strings. is inspired by the Smalltalk collection framework iteration protocols. started off as an open source project on GitHub called GS Collections. presented at JVM Language Summit(2012), JavaOne (2014) among several other impactful conferences. has several articles and performance benchmarks by authors as well as by users showing positive results.