You don't need to install Oracle Java with the installer version proposed on sweethome3d.com and SourceForge.net. Just double-click on the SweetHome3D file and it will run the program itself since there's no real installer program.
When you double-click on SweetHome3D, the system might prompt you to Run the program in a terminal or not. If it fails, run it in a terminal, and report here the issue that may appear in the terminal.