Self-created Minecraft plugin does not work?

I wanted to start programming Spigot server plugins with Eclipse Minecraft for version 1.13. I have now programmed a plugin that has not implemented anything yet, but it would have to be loaded on the local server anyway or enabled. However, it does not work, the error message in the server console reads:

Could not load 'plugins \ Ultramode.jar' in folder 'plugins'

I've been googling a lot, but nothing helped. Please help!

Maybe put off the semicolon behind "Ultramode" in the plugin.yml? You can also try packing the onEnable () method into the main. It would be best if you post the whole error.

Oh man, I'm so stupid… Yeah, the little bad semicolon was to blame.