> BoxPane does not automatically size its content to fill the available space.
More specifically, by default, a box pane gives each child component its preferred size. Since SplitPane does not have a preferred size, the box pane gives it a size of 0x0. Setting "fill" to true will cause a box pane to stretch its children to fit, but only in one direction. That's probably not what you want, so a TablePane is probably a better choice.
