将数据库中的数据输入到JTable出错

/*
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*/
package database_table;

import java.sql.*;
import javax.swing.JFrame;
import javax.swing.JScrollPane;
import javax.swing.JTable;

/**
*
* @author Administrator
*/
class database extends JFrame {

    JTable jt;
    JScrollPane js;
    Object data[][]=null;
    Object head[] = {"用户名", "密码"};

    public database() {

        super("数据库实例");
        this.connect();
        this.setVisible(true);
        this.setResizable(false);
        this.setSize(400, 300);
        this.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    }

    private void connect() {
        try {
            int rows = 0, index = 0;
            Connection con = DriverManager.getConnection("jdbc:odbc:mydatabase");
            Statement cmd = con.createStatement();
            ResultSet rs = cmd.executeQuery("select * from userlogin");
            while (rs.next()) {
                rows++;
            }
           data = new Object[rows][2];
           rs.beforeFirst();//beforeFirst 不是将光标移到第一行吗？为什么这里会抛出异常？？
            while (rs.next()) {
                data[index][0] = rs.getString(1);
                data[index][1] = rs.getString(2);
                index++;
            }
           
        } catch (SQLException ex) {
            //Logger.getLogger(database.class.getName()).log(Level.SEVERE, null, ex);
            System.out.println("数据库异常！");
        }
        jt = new JTable(data, head);
        js = new JScrollPane(jt);
        this.setContentPane(js);

    }
}

public class Main {

    /**
     * @param args the command line arguments
     */
    public static void main(String[] args) {
        // TODO code application logic here
        new database();
    }
}
我的红色部分是取得表的行数，但是当执行到绿色部分是就抛出异常了，想问一下这个地方该怎么做？
如果有更好的方法请贴上代码一起研究研究！
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问题解决了
Statement cmd = con.createStatement(ResultSet.TYPE_SCROLL_INSENSITIVE, ResultSet.CONCUR_READ_ONLY);这个地方要这样改就好了。
当时还有就是拖动那个表格的列名是会把两列交换位置，怎么设置才能让他们固定下来
----------------解决方案--------------------------------------------------------