Just want to mention that I’ve just published on GitHub an eclipse plug-in that builds Java desktop application projects into AppImage packages.
The project link is: https://github.com/brotenet/ide.export.appimage
At this point there is no Eclipse update-site for it available since this is part of a bigger project that I’m working on where I will be releasing an update-site once I’m done with all the plug-ins.
You can download the binary export using the link below -or- checkout the project source and build it in Eclipse RCP edition.
If you decide to try it then please let me know what you think, and if you found any bugs or things that I should be adding to it.