private boolean fequalsTreeAux(FTree other) {
    if (other == null) {
      return false;
    }
    if (!this.text.equals(other.text)) {
      return false;
    }

    boolean res = true;
    FTree left = this.getLeft();
    if (left != null) {
      res = left.fequalsTreeAux(other.getLeft());
    }
    if (res) {
      FTree sib = this.getSibbling();
      if (sib != null) {
        res = sib.fequalsTreeAux(other.getSibbling());
      }
    }
    return res;
  }