J2SM问题

我要2个界面，在第一界面完成后跳转到第二个界面，可是总是出现错误，第二界面不是空白的就是无法调用，求帮忙！第一个界面代码：private void jButton1ActionPerformed(java.awt.event.ActionEvent evt){
try
         {
             Connection con=DriverManager.getConnection(dbURL,userName,userPwd);
             Statement sql=con.createStatement();
             String uname=jTextField1.getText().trim();
             String passwd=jPasswordField1.getText().trim();
//             this.uName=jTextField1.getText().trim();
             String sel="select * from [User] where uName='"+uname+"'and Passwd='"+passwd+"'";
             ResultSet rs=sql.executeQuery(sel);
             if(rs.next())
             {
//                 new UpUaP2();
                 new UpUaP2(uname).setVisible(true);
                 this.hide();
                 con.close();
             }
             else
             {
                 System.out.println("<html><font color=#FF0000 size='4'>没有相关用户！请检查后再输入！</font>");
                 jTextField1.setText("");
                 jPasswordField1.setText("");
             }
         }
         catch(Exception e)
         {
             System.out.println("errCode: "+e.toString());
             System.out.println("err: "+e.getMessage());
         }}
第二界面代码：  public UpUaP2(String uName){}
 private void jButton2ActionPerformed(java.awt.event.ActionEvent evt) {                                         
        // TODO add your handling code here:
        System.exit(0);
    }                                            private void jButton1ActionPerformed(java.awt.event.ActionEvent evt) {                                         
        // TODO add your handling code here:
        加载驱动没问题，略去代码         
        try
         {
             Connection con=DriverManager.getConnection(dbURL,userName,userPwd);
             Statement sql=con.createStatement();
             String uname=jTextField1.getText().trim();
             String passwd=jTextField2.getText().trim();
             String upU="updata [User] set uName='"+uname+"'and Passwd='"+passwd+"' where uName='"+this.uName+"'";
             String upU2="updata [User] set Passwd='"+passwd+"' where uName='"+this.uName+"'";
             if(uname==" "||uname.equals(null))
             {
                 sql.execute(upU2);
                 System.out.println("更改成功！");
             }
             else
             {
                 sql.execute(upU);
                 System.out.println("更改成功！");
             }
         }
         catch(Exception e)
         {
             System.out.println("errCode: "+e.toString());
             System.out.println("err: "+e.getMessage());
         }在线等，急求解！！！！用的是NetBeans 的图形界面设计