JDiff is maybe also worth a mentioning.
JDiff is a Javadoc doclet which
generates an HTML report of all the
packages, classes, constructors,
methods, and fields which have been
removed, added or changed in any way,
including their documentation, when
two APIs are compared. This is very
useful for describing exactly what has
changed between two releases of a
product. Only the API (Application
Programming Interface) of each version
is compared. It does not compare what
the source code does when executed.
As I understood it runs on the sourcefolder of the old version and generates an xml file. The same for the sourcefolder with the new version. Than the two xml-outputs are compared and a changelist compiled. In html-javadoc-api-style