Is it possible to change default size of regions ( left, right, top, bottom ) of BorderPane regions ? In case of top and bottom change height and in case of top and bottom width?
I guess you mean "In case of top and bottom heigth changes and in case of left and right width changes?"
It seems not possible to set this sizes, but instead you can set preferredSize, maxSize, or minSize of the node of each of this regions, depending of the situation you want to prevent, as BorderPane regions resize to their Node size somehow. see "Resizable Range" in BorderPane doc.
Maybe you should edit your question and give more details.