The twitter API site lists 3 java twitter libraries.
Do you know others? What are your experiences in support, ease of use, stability, community, etc.
Answer
I just took a look at them.
JTwitter definitely looks like the weakest of the three. It doesn't appear to have been updated lately, doesn't cover much of the Twitter API, and doesn't appear to have any releases besides the initial one. On the upside, it's LPGL licensed, comes packaged with what little extra code it needs, and looks small and simple to understand.
The other two, java-twitter and Twtter4J look much closer in quality. Both cover the core API, and both have all the accouterments of normal open-source projects: publicly available source code repository, on-line docs, active mailing lists, and recent development activity.
However, Twitter4J looks to be the leader. From the docs, its API coverage appears to be more complete. The mailing list is definitely more active. The docs are much better. And most importantly to me, the releases have been more frequent. java-twitter has one release up, the "0.9-SNAPSHOT" release about 4 months ago. Twitter4J has had several releases in that time period, including 2.0.0 and incremental releases up through 2.0.8, fixing issues and adding support for new Twitter APIs.
I'm going to start with Twitter4J; if you don't hear back, assume it was just great for me.