Java HotSpot Virtual Machine

Hello,

sorry, I do not really know if this fits here, but maybe JNI can help
me solve my problem:
Under Visual C++ there are numerous examples of hooking into
another application, i.e. adding one's own menus to Notepad etc.

Is there a similar thing available for Java?
A net search has not resulted in anything useful.

What I would like to do:
1) Programmatically access the menu functions of a swing GUI in another 3rd party Java App for which I just have compiled classes, no source.
I know that awt.robot can do a bit, but I am looking for more:

2) Automatically extracting text from a Java Text Field of the 3rd party app (to repeat: I have no source code for this, therefore have to "hook" into the app from outside).
I have seen examples for C++ on codeguru, but nothing for Java.

3) A final challenge: adding my own menus to this 3rd party swing app. Again, possible in C++. I think impossible in Java.

Thanks so much for your help!

You are my last hope, literally.

Kind regards,
Tony