JAVA-登录功能完善

package com.itheima;

import javax.swing.*;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;

public class tologin {
    public static void main(String[] args) {
        JFrame jf=new JFrame();
        jf.setTitle("用户登录");
        jf.setSize(400,300);
        jf.setDefaultCloseOperation(3);
        jf.setLocationRelativeTo(null);
        jf.setAlwaysOnTop(true);
        jf.setLayout(null);        //取消窗体的默认布局

        //显示用户名文本
        JLabel usernameLabel=new JLabel("用户名");
        usernameLabel.setBounds(50,50,50,20);
        jf.add(usernameLabel);

        //用户名输入框
        JTextField usernameField = new JTextField();
        usernameField.setBounds(150,50,180,20);
        jf.add(usernameField);

        //显示密码文本
        JLabel passwordLabel=new JLabel("密码");
        passwordLabel.setBounds(50,100,50,20);
        jf.add(passwordLabel);

        JPasswordField passwordField = new JPasswordField();  //密码输入框用JPasswordField 加密显示
        passwordField.setBounds(150,100,180,20);
        jf.add(passwordField);

        //登录按钮
        JButton LoginButton=new JButton("登录");
        LoginButton.setBounds(50,200,280,20);
        jf.add(LoginButton);



        //已知的用户名和密码
        String name ="itheima";
        String pwd = "123456";

        //给登陆按钮添加一个事件
        LoginButton.addActionListener(new ActionListener() {
            @Override
            public void actionPerformed(ActionEvent e) {
                //获取用户输入的用户名和密码
                String username = usernameField.getText();//获取输入框输入内容
                String password = passwordField.getText();

                //先判断输入的用户名和密码是否符合要求
                //用户名和密码的长度都是6-12位
                if (username.length()<6 || username.length()>12){
//                    System.out.println("用户名的长度是6-12位,请重新输入");
                    JOptionPane.showMessageDialog(jf,"用户名的长度是6-12位,请重新输入");//窗口弹出文本提示
                    usernameField.setText("");//清空输入框内容
                }
                if (password.length()<6 || password.length()>12){
//                    System.out.println("密码的长度是6-12位，请重新输入");
                    JOptionPane.showMessageDialog(jf,"密码的长度是6-12位，请重新输入");
                    passwordField.setText("");
                }
                //在判断用户登录是否成功
                if (username.equals(name)&&password.equals(pwd)){
//                    System.out.println("登录成功");
                      JOptionPane.showMessageDialog(jf,"登陆成功");
                      usernameField.setText("");
                      passwordField.setText("");

                }else{
//                    System.out.println("用户名或密码有误");
                    JOptionPane.showMessageDialog(jf,"用户名或密码有误");
                    usernameField.setText("");
                    passwordField.setText("");
                }
            }
        });

        //添加按钮到窗体中
        jf.setVisible(true);


    }
}