...
Dim hbox As JavaObject
Dim priority As JavaObject
Dim b As Button
b.Initialize("button1")
b.Text = "Press Me"
b.PrefWidth = 200
hbox.InitializeNewInstance("javafx.scene.layout.HBox",Null)
priority.InitializeStatic("javafx.scene.layout.Priority")
hbox.RunMethod("setHgrow",Array(b,priority.GetField("ALWAYS")))
hbox.RunMethodJO("getChildren",Null).RunMethod("add",Array(b))
...