Now i'm running a clean and fresh installed Ubuntu 18.04, all works fine, except for sweethome3d...
Same limitations as in 17.10 if the program ist installed from the software center. no luck if i download it from here, then it is impossible to start sweethome3d.
For now it seems to me like the problem is not java, i beleve its the video drivers.
there are lots of improvements in other grafical software since 18.04, but not in sweethome3d on my machine...