protected int compareFolders(final Entry e1, final Entry e2) {
        final boolean f1 = e1 instanceof Folder;
        final boolean f2 = e2 instanceof Folder;
        
        if (f1 && !f2) {
            return -1;
        }
        else if (!f1 && f2) {
            return 1;
        }
        else {
            return 0;
        }
    }