Dear Florin,

To some extreme, you can start javafx first, then all other things will be transfered to Java afterwards. Like this:

JavaMain.java

public class JavaMain {
  public static Object start( JavaInterface ji){
    return ji.createStage();
  }
}

JavaInterface.java

public interface JavaInterface {
  public Object createStage();
}

MyStage.fx

public class MyStage extends JavaInterface {

  public override function createStage(): Object{

    Stage {
      title: "Application title"
      width: 250
      height: 80
      scene: Scene {
        content: Text {
          font: Font {
            size: 24
          }
          x: 10,
          y: 30
          content: "Application content"
        }
      }
}
  }

Main.fx

var mys = MyStage{};
JavaMain.start(mys);