ObjectAid was a very useful Eclipse plug-in which generates class diagram from your source code.
Unfortunately it looks like it is discontinued in March 2022 or at least its website is not working.
I've been able to install an old version of ObjectAid. Here is what I did:
You can also download version 1.2.4 which works with Java 17 and Eclipse 2022-03 (4.23.0) but then you must follow the instructions from this answer to be able to run it.