I didn't try under Ubuntu 15 yet, but under Ubuntu 14 and Java 8u60, the bug is still here:
- select Floor color or texture option in Sweet Home 3D preferences
- draw a room
- modify the room, choosing a texture for its floor.
Try to resize the window or the plan, and you'll see the plan isn't drawn anymore.
Please report if you see the same issue under Ubuntu 15.

As Oracle closed this bug, I fear it will take long before it's got fixed, unless it's an error in Ubuntu graphics layer. If there's nothing new about this bug in a few months, I'll simply disable floor textures under Linux when the program is run with Java 7/8.