The anonymous inner class is not released here, causing a memory leak.
anchorPane is an AnchorPane, while grandParentButton and someButtonInsideAnchorPane are Buttons.

anchorPane.getParent().getParent().lookup("#grandParentButton").addEventFilter(KeyEvent.KEY_PRESSED, new EventHandler<KeyEvent>() {
        @Override
        public void handle(KeyEvent e) {
            if (e.getCode() == KeyCode.ENTER) {
                someButtonInsideAnchorPane.requestFocus();
                e.consume();
            }
        }
    });