This kind of question is much better asked on a proper Q&A site like programmers.stackexchange.com, not a news site like HN.

Eclipse, Netbeans and IntelliJ all have strong user/fan-bases. Those might be a good place to start. (note: IntelliJ is only free for some editions and types of development).

IntelliJ Idea Ultimate is by far my favorite Java IDE. The community version (free version) is still good and updates are frequent, but you don't get as much of the "I" in IDE.

Eclipse is free and has a huge user base, lots of plugins, and people even build full applications on top of the open platform.

JCreator http://www.jcreator.com/

I think it is the only decent Java IDE not written in Java. From the site: "JCreator is written entirely in C++, which makes it fast and efficient compared to the Java based editors/IDE's."

IntelliJ IDEA Community Edition

http://www.jetbrains.com/idea/

Eclipse works well, is free and has good community support.

Netbeans