I did my dissertation on Java3D available for windows and linux
(blackdown). Java3D is a very good library of graphics routines. I
advise that you follow the tutorials that come with J3D and practice on
their demo files.

Autocad is a 2D program that has a 3D renderer when selected. There
should be no problem creating  a similar program using Swing/AWT.
However, if you want 3D graphics in java  use the Java3D library or use
GL4Java, which is slightly more complex.