//用户登录的代码:
//LoginFrame.java
import javax.swing.*;
import java.awt.*;
import java.awt.event.*;
 
class MyJPanel extends JPanel implements ActionListener{
       private int count=0;       
       private JLabel label1,label2;
       private JTextField text;
       private JPasswordField pass;
       private JButton button1,button2;   
       MyJPanel(){
              label1=new JLabel("用户名");
              label2=new JLabel("密码");
              button1=new JButton("确定");
              button2=new JButton("取消");
              text=new JTextField(20);
              pass=new JPasswordField(20);
              button1.setMnemonic(KeyEvent.VK_O);//设置按钮快捷键
              button2.setMnemonic(KeyEvent.VK_C);
              button1.setActionCommand("entry");
              button2.setActionCommand("cancel");
              button1.addActionListener(this);//注册按钮事件
              button2.addActionListener(this);//注册按钮事件
              setBackground(Color.cyan);//设定面板背景色
              add(label1);
              add(text);
              add(label2);
              add(pass);
              add(button1);
              add(button2);
       }
       
       public void actionPerformed(ActionEvent e){
              if (e.getActionCommand().equals("entry")){
                     count++;  //计数
                     String username,password;
                     if (count<3) {
                            username=text.getText();
                            password=pass.getText();
                            if (username.equals("abcd")&&password.equals("123456")){
                                   text.setText("用户名及密码正确!");
                                   pass.setText("");                          
                            }
                            else{
                                   text.setText("");
                                   pass.setText("");                          
                            }
                     
                     }
                     else
                            System.exit(0);//退出程序
              }
              else 
                     System.exit(0);//退出程序
       }
}
 
public class  LoginFrame extends JFrame {
       public static void main(String[] args) {
              MyJPanel jp=new MyJPanel();//定义面板
              jp.setBorder(BorderFactory.createTitledBorder("输入用户名和密码"));//设定边界
              JFrame frame=new JFrame("用户登录");
              frame.setSize(300,150);
              frame.setContentPane(jp);//在框架中加载面板
              frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);//设置框架关闭按钮事件
              frame.setVisible(true);
       }
}