Scala How to change window size - scala

Question

I would like to change the size of my window application. I am using scene builder for this project. In the preview, the size of my fxml is the size that I want. However, when I try to run it with my windows it will show the application in a slightly small size. My question is how can I make the window application size the same as the size of the preview. In another word, I want to make my window application to the exact size that I want. Below attach my code.
import scalafx.application.JFXApp
import scalafx.application.JFXApp.PrimaryStage
import scalafx.scene.Scene
import scalafx.Includes._
import scalafxml.core.{NoDependencyResolver, FXMLView, FXMLLoader}
import javafx.{scene => jfxs}
import scalafx.scene.image.Image
object MainApp extends JFXApp {
// transform path of RootLayout.fxml to URI for resource location.
val rootResource = getClass.getResource("view/RootLayout.fxml")
// initialize the loader object.
val loader = new FXMLLoader(rootResource, NoDependencyResolver)
// Load root layout from fxml file.
loader.load();
// retrieve the root component BorderPane from the FXML
val roots = loader.getRoot[jfxs.layout.BorderPane]
// initialize stage
stage = new PrimaryStage {
title = "TalkShow"
scene = new Scene {
root = roots
}
}
// actions for display person overview window
def showTalkOverview() = {
val resource = getClass.getResource("view/TalkShow.fxml")
val loader = new FXMLLoader(resource, NoDependencyResolver)
loader.load();
val roots = loader.getRoot[jfxs.layout.AnchorPane]
this.roots.setCenter(roots)
}
def showWelcome() = {
val resource = getClass.getResource("view/Welcome.fxml")
val loader = new FXMLLoader(resource, NoDependencyResolver)
loader.load();
val roots = loader.getRoot[jfxs.layout.AnchorPane]
this.roots.setCenter(roots)
}
// call to display PersonOverview when app start
showWelcome()
}