sybase与jtree的连接的问题。。。

代码用的是这样的，但是报了java.sql.SQLException: JZ0BT: 类型 TYPE_FORWARD_ONLY 的 ResultSets 不支持 relative(int) 方法。的错误；

package jtree;

import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;

import javax.swing.JFrame;
import javax.swing.JTree;
import javax.swing.tree.DefaultMutableTreeNode;

public class Main2 extends JFrame   
{   
  private static Connection con;   
  private static Statement ste = null;   
  ResultSet rs;   
  // 连接数据库   
  static   
  {   
  String driver = "com.sybase.jdbc2.jdbc.SybDriver";   
  String connection = "jdbc:sybase:Tds:127.0.0.1:2638/yongyiGdzc?charset=cp936";   
  // 数据库用户名   
  String user = "dba";   
  // 数据库密码   
  String password = "sql";   
  try   
  {   
  Class.forName(driver);   
  }   
  catch (ClassNotFoundException e)   
  {   
  // TODO Auto-generated catch block   
  e.printStackTrace();   
  }   
  try   
  {   
  con = DriverManager.getConnection(connection, user, password);   
  }   
  catch (SQLException e)   
  {   
  // TODO Auto-generated catch block   
  e.printStackTrace();   
  }   
  try   
  {   
  //ste = con.createStatement(ResultSet.TYPE_SCROLL_SENSITIVE, ResultSet.CONCUR_UPDATABLE);  
  ste = con.createStatement();  
  }   
  catch (SQLException e)   
  {   
  // TODO Auto-generated catch block   
  // e.printStackTrace();   
  }   
  }   
   
  Main2()   
  {   
  DefaultMutableTreeNode node = new DefaultMutableTreeNode("root");   
  createNodes(node, "0");   
  JTree tree = new JTree(node);   
  add(tree);   
  setSize(200, 200);   
  this.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
  setVisible(true);   
  }   
   
  public static void main(String[] argv) throws Exception   
  {   
  new Main2();   
   
  }   
   
  public void createNodes(DefaultMutableTreeNode parent, String ParentID)   
  {   
  DefaultMutableTreeNode temp = null;   
  String strsql = "select Unitid,unitname,companyname from Unit where companyname ='" + ParentID + "'";   
  // 光标的相对位置   
  int i = 0;   
  try   
  {   
  rs = ste.executeQuery(strsql);   
  while (rs.next())   
  {   
  i++;   
  temp = new DefaultMutableTreeNode(rs.getString("unitname"));   
  parent.add(temp);   
  String gj=rs.getString("Unitid");
  createNodes(temp, gj);   
  System.out.println(""+gj+"--------"+i);
  rs = ste.executeQuery(strsql);   
  // 重新定位光标   
  rs.relative(i);   
  }   
  }   
  catch (Exception e)   
  {   
  System.out.println(e);   
  }   
  }   
}