How to save Document object into .xml file

1) Iam converting JDBC ResultSet into XML.

2) Iam done with converting JDBC ResultSet to Document.

3) My query is, how can I save it into a .xml file using FileOutPutStream. For your perusal I've attached the code.

4) I've converted it into string and stored in xml file. But I don't find any wellformed xml content in the xml file

public Document getCustomerList()
{
      Document document = null;
      try
      {
            statement = connection.createStatement();
            resultset = statement.executeQuery("select *from temp");
            document = toDocument(resultset);
            resultset.close();
            statement.close();
      }
      catch(Exception e)
      {
            e.printStackTrace();
      }
      return document;
}

public Document toDocument(ResultSet resultset) throws ParserConfigurationException, SQLException
{
      DocumentBuilderFactory factory = DocumentBuilderFactory.newInstance();
      DocumentBuilder builder = factory.newDocumentBuilder();
      Document document = builder.newDocument();
      ResultSetMetaData rsmd = resultset.getMetaData();
      int colCount = rsmd.getColumnCount();

      Element results = document.createElement("Results");
      document.appendChild(results);
      while(resultset.next())
      {
            Element rows = document.createElement("Rows");
            results.appendChild(rows);

            for(int i = 1;i <= colCount;i++)
            {
                  String columnName = rsmd.getColumnName(i);
                  Object value = resultset.getObject(i);
                  Element node = document.createElementcolumnName);
                  node.appendChild(document.createTextNode(value.toString()));
                  rows.appendChild(node);
            }
      }
      return document;
}

public static void main(String[] args) throws Exception
{
      JavaXML jxml = new JavaXML();
      Document document = jxml.getCustomerList();

      byte buffer[] = (document.toString()).getBytes();
      OutputStream xmlfile = new FileOutputStream("xmlfile.xml");
      xmlfile.write(buffer);
      xmlfile.close();

}