@Override
    public void setSelectedItem(Object object) {
        if (object instanceof String) {
            for (HistoryElement element : history) {
                if (object.equals(element.expression)) {
                    object = element;
                    break;
                }
            }
        }
        if (object instanceof String) {
            object = selectedItem.changeExpression((String)object);
        }
        if (selectedItem != null && selectedItem != object || selectedItem == null && object != null) {
            selectedItem = (HistoryElement)object;
            fireContentsChanged(this, -1, -1);
        }
    }
@Override
    public void setSelectedItem(Object object)