Why do I get so many errors?

[Naadiyaar]

Here I've downloaded JakartaEE-mail source code to study it locally, but nvim-jdtls is showing tons of different errors and warning. However the project compiles with no issue. Any idea what's the problem?
screenshot from mail-api/api/src/main/java/jakarta/mail/Transport.java :

Link to project:
https://github.com/jakartaee/mail-api/tree/master

Edit: it worth mentioning that the plugin is working fine in general and I'm facing this issue only with this project

[rogeriofrsouza]

I've seem these errors as well.
I don't know much about it, seems like multi-modules projects requires some LSP config.
Btw, the new Eclipse Angus Mail project doesn't have these same errors.