So I had a 10000 lines code file, and Emacs would just crash or not do much.
That's suprising. What version of Emacs was this and what kind of machine did you have? How did you configure it? Anything capable of running Eclipse should have no problem running Emacs. And as far as clicking on methods and jumping to places in the code goes, Emacs+etags (and M-x visit-tags-table) have been doing that pretty well for the past 15 years.
It was maybe 5 years ago, and I was probably running that Java IDE "plugin" for Emacs, too. Might have been version 18.x, and a computer with 600MhZ CPU, 256MB RAM.
I know about etags, but that is just the thing: you have to set it up and run it regularly. Also, it did not work as well as an IDE that really understands the code (etags don't understand the code). At least that was my impression - my "jumps" in Emacs would frequently lead to the wrong place.
Edit: also, what I meant for navigation was the code outline. In an IDE, you get an extra window listing only the methods you defined in your code. You can click on a method and jump right to the code. The IDE thing for emacs did that, too, but not as nicely (it was in a weird sidebar without proper scrollbars, for one thing).
That is also a Java sickness of course, that there are zillions of interfaces and abstract classes with the same name (BlubInterface, AbstractBlubBase, BlubImpl). But Eclipse then gives you a popup where you can select the proper class (showing the classes hierarchically).
That's suprising. What version of Emacs was this and what kind of machine did you have? How did you configure it? Anything capable of running Eclipse should have no problem running Emacs. And as far as clicking on methods and jumping to places in the code goes, Emacs+etags (and M-x visit-tags-table) have been doing that pretty well for the past 15 years.