If you can live without an Eclipse plugin and use a standalone program, check out ArgoUML (tigris.org) or its commercial enhancement Poseidon (gentleware).
There are one or more UML plugins for Eclipse, but the standalone UML apps are more full-featured. ArgoUML can do reverse engineering of
Java code. Poseidon comes in 2 flavours, community (free) and commercial (not free), but only the commercial version of Poseidon can do reverse engineering.