Eclipse: remove plugins that fail to load

Question

Whenever I start my copy of Eclipse, I get the following error message:

I'm not interested in those plugins (I can't use Java 8 anyway, for reasons I won't bore you with) so there's no point in having them installed.

I went to the Help --> Installation Details menu (as suggested in various posts here on SO), but there seems to be no option to uninstall a plugin, you can only see the list of plugins and view their signature / copyright info, as you can see:

The only tab that has a "uninstall" menu option is the first one ("Installed software") but it only contains eclipse stuff and a couple of other addons I installed that have nothing to do with the ones I want to remove.

So, what am I missing here?

Answer 1

Here's what worked for me on eclipse Neon:

Step 1: Uninstall...

After "Uninstall", the some stuff is still registered and listed in "Plug-ins" under Installation Details. There is no option to uninstall or delete plug-ins in that view.

The following steps are outside eclipse

Step 2: Delete plug-in files from .p2/pool/ directory (plugins and features)

Result: The plugins were no longer registered or listed in "Plug-ins" list. Start-up showed annoying errors about icons that are not found.

Step 3: start eclipse with -clearPersistedState option

The missing icons error disappeared, but it was not possible to install the plugin again: Eclipse had registered somehow that the plugin was already downloaded and complained that the files were missing instead of downloading them again.

Step 4: Clean references to plugin from .p2/pool/artifacts.xml

Didn't really help, plugin could still no be installed. Not sure if this step is any good.

Step 5: Clean cache from .eclipse directory, primarily from .eclipse/org.eclipse.oomph.p2/cache

After clearing a number of directories in .eclipse, primarily caches, I was able to install the plugin again.

Maybe step 4 or 5 could be replaced by hitting "Reload" in the "Available Software Sites" preferences view?