java图形用户界面（登录界面）

import javax.swing.JFrame;
/**
 *
 *用户登录页面程序
 *
 */
import java.awt.*;
import javax.sound.midi.VoiceStatus;
import javax.swing.*;
import java.awt.event.*;
public class MyFieldExample extends JFrame implements ActionListener{
JLabel jL1,jL2,jL3;
JButton jB1,jB2;;
JTextField jF1;
JPasswordField jP1;
private int i=3;//定义只可以输入3次
  public MyFieldExample()
    {
      super("文本框/密码框综合应用");
      jL1=new JLabel("用户名称");
      jL1.setBounds(15,5,60,20);
      jL2=new JLabel("登录密码");
      jL2.setBounds(15,25,60,20);
      jF1=new JTextField("",20);
      jF1.setBounds(110,5,100,20);
      jP1=new JPasswordField("",20);
      jP1.setBounds(110,25,100,20);
      jB1=new JButton("确定");
      jB1.setBounds(35,50,60,30);
      jB1.addActionListener(this);
      jB2=new JButton("取消");
      jB2.setBounds(130,50,60,30);
      jB2.addActionListener(this);
      jL3=new JLabel("");
      jL3.setBounds(60,90,200,30);
    Container winContainer=this.getContentPane();
    winContainer.setLayout(null);
    winContainer.add(jL1);
    winContainer.add(jL2);
    winContainer.add(jL3);
    winContainer.add(jF1);
    winContainer.add(jP1);
    winContainer.add(jB1);
    winContainer.add(jB2);
    this.setSize(300,200);
    this.setVisible(true);
    this.setLocation(300,300);
    this.setDefaultCloseOperation(WindowConstants.DISPOSE_ON_CLOSE);
    }
  public static void main(String[] args)
    {
      MyFieldExample w1=new MyFieldExample();
    }
  public void actionPerformed(ActionEvent e)
    {
      i--;//每次点击时进行-1
      if(e.getSource()==jB1)
      {
          if(jF1.getText().equals("JAVA")&&jP1.getText().equals("1234"))
            jL3.setText("输入正确,登录成功");
          else{
            if(i==0) {//当是0时，我们就无法再次输入了
              jL3.setText("请速与管理员联系");
              System.exit(0);
            }else{
              jL3.setText("输入错误,登录失败,你还剩"+(i)+"次");//提示还有几次机会
            }
        }
      }else if(e.getSource()==jB2)
        System.exit(0);
    }
}