I am writing a G-code generator in java...(as I'm more comfortable with it). I will try to integrate these elements through that piece of code. I hope it works out....to integrate java into such an environment.
You can create the code that is going to be executed at each of the co-ordinates, any way you like. If you output it to
/tmp/operation.ngc it will be used by my splice code, or you can write your own
program entirely to do the same thing as splice.
What you won't be able to do is write a hal component in java. The libraries are written in C, with python bindings written in C to allow python to use them.
If you want to execute a java program, you will probably have to do it from a script, the same way that initially splice was executed.
however I am not sure if its possible to call a java class that creates something like a pop-up window with buttons,numbers etc
I know little about java, I looked at it for web programming a long time back but never continued with it.
Dialogs with data fields etc will be bread and butter stuff, it just depends how you are intending to activate them.
regards