When using the default classpath entry preference page (under "runtimes" in the preference page section), use the combo to select some runtime type like as7. When the viewer fills up, note the following:

1) Click on an entry in the middle (not top or bottom entry): NPE
2) Click 'add' - note "name" entry is not used, confusing for a user
3) Click 'add' - note default folder is blank and not useful
4) Click 'add' - note that titles and descriptions are not very good
5) Click 'add' - note that default includes pattern is */.xml, not relevant for classpath