Gavin Clarke at The Register reported that the “library includes new collection types for Multimap, Multiset, and Bitmap, a MapMaker builder for concurrent hash maps, and an Ordering collection Google described as ‘Comparator on steroids.'”
It’s all about convenience.
“The library’s functionality simplifies your code so it’s easier to write, read, and maintain,” Google’s Jared Levy told JavaLobby. “The Google Collections Library will improve your productivity as a developer, while reducing the amount of boilerplate low-level code you need to write.”