While trying to build an older release (0.20.0) in Eclipse, I came across a thread in the archives from a few months ago describing the same problem I was having. It's unresolved on the list and though I found a solution, I wasn't subscribed to common-dev at the time and so I can't reply to it.
http://mail-archives.apache.org/mod_mbox/hadoop-common-dev/200911.mbox/%3c911071.77113...@web57202.mail.re3.yahoo.com%3e I saw the same set of errors, though with 0.20.0 instead of 0.20.1. I believe this was a build path issue. Changing src/benchmarks to src/benchmarks/gridmix2/src/java fixed it for me. Hopefully this helps someone else trying to setup Eclipse with an older release. Ed
