@Override
   public String toString() {
      StringBuffer b = new StringBuffer();
      List<Tnode> usedList = new ArrayList<>();
      Tnode current = this;

      do {
         if (!usedList.contains(current)) {
            b.append(current.getName());
            usedList.add(current);
         }

         Tnode child = current.getFirstChild();
         Tnode sibling = current.getNextSibling();

         if (child != null) {
            if (child.getNextSibling() != null || child.getFirstChild() != null) {
               current = current.getFirstChild();
            } else {
               current.setFirstChild(null);
               current = this;
            }
            if (!usedList.contains(current)) {
               b.append("(");
            }
         } else if (null != sibling) {
            if (sibling.getFirstChild() != null) {
               current = current.getNextSibling();
            } else {
               current.setNextSibling(null);
               if (!usedList.contains(sibling)) b.append(",").append(sibling.getName());
               current = this;
               b.append(")");
            }
            if (!usedList.contains(current)) {
               b.append(",");
            }
         }
      } while (this.getFirstChild() != null);
      return b.toString();
   }