public void setHierarchyRoots(Set roots, boolean flat)
public void setHierarchyRoots(Set roots, boolean flat, boolean refresh)
    public void setHierarchyRoots(Set roots, boolean flat)    {        if (model.getState() != LOADING_HIERARCHY)            throw new IllegalStateException(                    "This method can only be invoked in the LOADING_HIERARCHY "+                    "state.");                model.createBrowser(roots, flat);        model.createClipBoard();        model.getClipBoard().addPropertyChangeListener(controller);        model.fireThumbnailLoading();        //b/c fireThumbnailLoading() sets the state to READY if there is no        //image.        if (model.getBrowser().getImages().size() == 0) setStatus("Done", -1);        else setStatus(HiViewer.PAINTING_TEXT, -1);        fireStateChange();    }