You can install springboot-nvim and add nvim-java as a dependency instead of jdtls. Like this:

Then to make the plugin register non springboot projects you can edit the plugin a little. Go to ~/.local/share/nvim/lazy/springboot-nvim/lua/springboot-nvim, and open the utils.lua file. In the file you will find a function called "find_main_application_class_directory". Edit it to look like this:

Now you can setup keybindings for generating new classes, enums and interfaces in java projects. Here are mine for referance, with a function so they are only available when jdtls is attached to the buffer . Its missing some keymaps, made it today so i havent finished.

A bit late but i hope you still find it useful!

I know this thread is old, but I had the same need and I created a separate plugin from this one that serves only that purpose.
If you want, you can find it here:
https://github.com/alessio-vivaldelli/java-creator-nvim