This is "Auto Java Complete".
When you edit a java file or jsp file ,it can dropdown a menu to show
the candidates using auto-complete and yasnippet.
read ajc-java-complete.el for more info.
page on emacswiki:

http://www.emacswiki.org/emacs/AutoJavaComplete

you can download a Video demo (2.8M ,5M)
http://screencast-repos.googlecode.com/files/auto-java-complete-demo-editing-jsp-2011-01-20.mp4
http://screencast-repos.googlecode.com/files/auto-java-complete-demo-2010-12-25.mp4.bz2