Java SE (Java Platform, Standard Edition)

I know how add new button to HTMLEditor, and I want set to my button action to paste some text in the current cursor position.

//HTMLEditor html;
//String IMAGE_URL = "http://...";
Node node = html.lookup(".top-toolbar");
if (node instanceof ToolBar) {
   ToolBar bar = (ToolBar) node;
   ImageView graphic = new ImageView(new Image(IMAGE_URL, 32, 32, true, true));
   Button myButton = new Button("", graphic);
  bar.getItems().add(myButton);
  myButton.setOnAction(new EventHandler<ActionEvent>() {
   @Override
   public void handle(ActionEvent arg0) {
   //needs code
   }
   });
}