用户登录怎么怎么核对用户信息

import java.awt.*;import java.awt.event.*;import javax.swing.*;//主窗口部分class Window extends JFrame implements ActionListener{    JTextField cardnumber;        /*卡号*/    JPasswordField password;     /*密码*/    JButton b1,b2;        public Window(){       super("欢迎进入银行系统");       Container cont=getContentPane();       cont.setLayout(new FlowLayout());       cont.add(new JLabel("卡号"));       cardnumber=new  JTextField(10);       cont.add(cardnumber);       cont.add(new JLabel("密碼"));       password=new JPasswordField(10);       password.setEchoChar('*');              cont.add(password);       b1=new JButton("确定");       b2=new JButton("退卡");       cont.add(b1);       b1.addActionListener(this);       cont.add(b2);       b2.addActionListener(this);       this.addWindowListener(new WindowAdapter(){       //完全关闭窗口            public void windowClosing(WindowEvent e){                System.exit(0);                }            });       setBounds(120,125,200,175);       setVisible(true);              }// public window           public void actionPerformed(ActionEvent e){           if(e.getActionCommand().equals("确定")){               if(cardnumber.getText().equals(123456)&&password.equals(123456))                   JOptionPane.showMessageDialog(null, "yes");                else                   JOptionPane.showMessageDialog(null, "信息输入错误");                     }                   //if                if(e.getActionCommand().equals("退卡"))                    System.exit(0);       //退卡                           }//actionPerformed               }//windowpublic class ATM{    public static void main(String args[]){        new Window();    }}