The google-collections based version causes test-tools to hang running the tethering test, a bit of multi-threaded Avro. There could well be bugs in the tethering code that use of google's concurrent hashmap somehow brings out, but I didn't take the time to debug that.
Google collections 1.0 is also incompatible with checkstyle, which needs google-collections 0.9. So, until checkstyle 5.1 is available in a maven repo, if we use google collections, then we need to use 0.9.
Here's a new version that doesn't rely on google collections for the above reasons. The tethering test passes and checkstyle works, but it's a bit slower:
GenericReaderOneTimeUsageTest: 2264 ms, 1.839572825273033 million entries/sec. 0.008609545204085958 million bytes/sec
I also tried using an equals hashmap, and things slow to around 3800 milliseconds. Also, folks should not directly compare my timings with Kevin's: my laptop seems about 35% slower than whatever Kevin uses. If that's right, this latest version should be a bit faster than 1.2.