B4J Code Snippet Visible rows in a control

@SuppressWarnings("restriction")
    private int first =0;
    private int last = 0;

    public void getFirstAndLast(TableView<?> t){
        TableViewSkin<?> ts = (TableViewSkin<?>) t.getSkin();
        VirtualFlow<?> vf = (VirtualFlow<?>)ts.getChildren().get(1);
        first = vf.getFirstVisibleCell().getIndex();
        last = vf.getLastVisibleCell().getIndex();
    }
    public int getFirst(){
        return first;
    }
    public int getlast(){
        return last;
    }

    ' t,tvs and vf defined as JavaObject
    tvs.InitializeStatic("com.sun.javafx.scene.control.skin.TableViewSkin") ' JavaObject
    vf.InitializeStatic("com.sun.javafx.scene.control.skin.VirtualFlow") ' JavaObject
    t = table1 ' TableView to look at
    tvs = t.RunMethodJO("getSkin",Null) '  get skin from TableView
    vf = tvs.RunMethodJO("getChildren",Null).RunMethodJO("get",Array As Object(1)) ' get virtual flow from skin
    first = vf.RunMethodJO("getFirstVisibleCell",Null).RunMethod("getIndex",Null) ' get first from virtual flow
    last = vf.RunMethodJO("getLastVisibleCell",Null).RunMethod("getIndex",Null) ' get last from virtual flow
    Log("First: "& first & " Last: " & last) ' just display values

    ' l,lvs, vf as JavaObject
    lvs.InitializeStatic("com.sun.javafx.scene.control.skin.ListViewSkin") ' JavaObject
    vf.InitializeStatic("com.sun.javafx.scene.control.skin.VirtualFlow") ' JavaObject
    l = list1 ' ListView to look at
    lvs = l.RunMethodJO("getSkin",Null) '  get skin from ListView
    vf = lvs.RunMethodJO("getChildren",Null).RunMethodJO("get",Array As Object(0)) ' get virtual flow from skin
    first = vf.RunMethodJO("getFirstVisibleCell",Null).RunMethod("getIndex",Null) ' get first from virtual flow
    last = vf.RunMethodJO("getLastVisibleCell",Null).RunMethod("getIndex",Null) ' get last from virtual flow
   Log("First: "& first & " Last: " & last) ' just display values