As the subject says: how do I hide the mouse cursor in fullscreen mode?
Replace the cursor with a custom cursor created from an empty transparent image.
setCursor(getToolkit().createCustomCursor(new BufferedImage(1,1,BufferedImage.TYPE_INT_ARGB),new Point(0,0),null));
Toolkit.getDefaultToolkit().createCustomCursor(Toolkit.getDefaultToolkit().createImage(""), new Point(), null);