public String toString(){
  StringBuilder buf=new StringBuilder();
  buf.append("<root>");
  toStringHelper(root,buf,1);
  return buf.toString();
}

public String toString ( ) { StringBuilder buf = new StringBuilder ( ) ; buf . append ( "<root>" ) ; toStringHelper ( root , buf , 1 ) ; return buf . toString ( ) ; }
returns a string representation of the tree state of this , i . e . , the concrete state . ( the version of tostring commented out below returns a representation of the abstract state of this .
