For me as a single developer on the project, which is admittedly a very small project, there have been remarkably few changes to Class Viewer since 2004. As GUI is the same, while menu has changed a bit, mainly with introduction of Command option. Also originally for some reason I called the XML configuration file packagedirectory.xml but now is more appropriately ClassViewerConfig.xml, and it has some additional internally handling a few new features.
And biggest new features over more than a decade was option to open a class at startup with a command line option, and ability to open a Java file instead of going to JavaDocs.
And Java language forced changes have been minimal with biggest coming with Java 8 and shift in how to access html of JavaDocs.
Spanning over a decade Class Viewer is in essence same thing as was back in 2004, with just a few changes. Does make it easier to maintain.