以java实现的一个简单登录界面（带验证码）

import java.awt.*;//导入awt包
import javax.swing.*;//导入swing包
import java.awt.event.ActionListener;//导入awt包中的监听器事件包
import java.awt.event.ActionEvent;//导入awt包中的ActionEvent事件包

public class EnterScreen extends JFrame {
    static int s=0;
    public EnterScreen() {
        Yanzhencode vcode = new  Yanzhencode();
        setSize(300,290);//设计窗体的大小
        setTitle("请登录");
        setBackground(Color.RED);//设置背景颜色
        JLabel a=new JLabel("登录名"); //实例化JLabel对象
        JLabel b=new JLabel("密    码");
        JLabel g=new JLabel("忘记用户名/密码？");
        JLabel h=new JLabel("验证码");
        g.setForeground(Color.BLUE);
        JTextField c=new JTextField(15);//实例化用户名文本框
        JPasswordField d=new JPasswordField(15);//实例化密码框
        JTextField k=new JTextField(4);//实例化验证码框
        d.setEchoChar('*');//将输入密码框中的密码以*显示出来
        JButton e=new JButton("登录");
        JButton f=new JButton("快速注册");
        e.setBackground(Color.YELLOW);//设置登录按钮字体颜色
        f.setForeground(Color.GRAY);//设置快速登录按钮填充色
        setVisible(true);//使窗体可视化
        Container m=getContentPane();//获取一个容器
        getContentPane().setBackground(Color.WHITE);//设置窗体填充色
//        将用户名、密码的Jlabel和用户名JTextField文本框、密码JPasswordField密码框以及确定JButton、快速注册JButton添加到container容器里面                         //
        m.add(a);
        m.add(b);
        m.add(c);
        m.add(d);
        m.add(e);
        m.add(f);
        m.add(g);
        m.add(h);
        m.add(k);
        m.add(vcode);
        setBounds(300,300,300,300);//设置窗体的长宽各为300、300  让其显示在左上方的300、300处
        m.setLayout(null);
//        a、b、c、d、e、f显示在container容器中的位置坐标
        a.setBounds(10,40,50,18);
        b.setBounds(10,80,50,18);
        c.setBounds(60,40,130,18);
        d.setBounds(60,80,130,18);
        h.setBounds(10,120,50,18);
        k.setBounds(60,120,80,18);
        e.setBounds(90,180,100,30);
        f.setBounds(90,220,100,30);
        g.setBounds(190,75,100,30);
        vcode.setBounds(140,110,80,30);
        e.addActionListener(new ActionListener() {//对登录按钮添加监听事件

            @SuppressWarnings("deprecation")
            @Override
            public void actionPerformed(ActionEvent arg0) {
                // TODO Auto-generated method stub

                if(c.getText().trim().equals("xiaoyang")&&new String(d.getPassword()).equals("123456")&&s==1) {//equals函数进行用户名和密码的匹配
                    JOptionPane.showMessageDialog(null,"登录成功");

                    new NewFrame();//进入到NewFrame这个窗体中
                }else if(c.getText().trim().equals("xiaoyang")&&new String(d.getPassword()).equals("123456")&&s==0) {
                    JOptionPane.showMessageDialog(null,"验证码输入错误");
                }else {
                    JOptionPane.showMessageDialog(null, "登录失败,用户名、密码或验证码输入错误");
                }
            }

        });
        f.addActionListener(new ActionListener(){//对快速注册按钮添加监听事件
            @SuppressWarnings("deprecation")
            @Override
            public void actionPerformed(ActionEvent arg0) {
                // TODO Auto-generated method stub
                new zhuce();//进入都到zhuce窗体中
            }

        });
        //判断输入验证码是否正确
            if(k.getText()== null) {
                s=0;
            }else if(vcode.getCode() == null) {
                s=1;
            }else if(vcode.getCode() .equals(k.getText())) {
                s=1;
            }else {
            s=0;
        }
    }

        public static void main(String[] args) {
            new EnterScreen();

        }

    }

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

import javax.swing.JButton;
import javax.swing.JLabel;
import javax.swing.JPasswordField;
import javax.swing.JTextField;

public class zhuce extends JFrame {
    public zhuce() {
        setSize(300,250);//设计窗体的大小
        JLabel a=new JLabel("用户名"); //实例化JLabel对象
        JLabel b=new JLabel("密    码");
        JLabel h=new JLabel("再次确认密码");
        JTextField c=new JTextField(15);//实例化用户名文本框
        JPasswordField d=new JPasswordField(15);//实例化密码文本框
        JPasswordField hd=new JPasswordField(15);//实例化密码文本框
        d.setEchoChar('*');//设置密码隐藏制度
        JButton e=new JButton("确定");
        JButton f=new JButton("重置");
        JButton g=new JButton("返回");
        setVisible(true);
        //获取一个容器
        Container m=getContentPane();
//        将用户名、密码的Jlabel和用户名JTextField文本框、密码JPasswordField密码框以及确定JButton、快速注册JButton添加到container容器里面
        m.add(a);
        m.add(b);
        m.add(h);
        m.add(hd);
        m.add(c);
        m.add(d);
        m.add(e);
        m.add(f);
        m.add(g);
        //设置窗体的长宽各为300、250  让其显示在左上方的300、250处
        setBounds(300,250,300,250);
        m.setLayout(null);
//        a、b、c、d、e、f显示在container容器中的位置坐标
        a.setBounds(10,40,50,18);
        b.setBounds(10,80,50,18);
        h.setBounds(5,120,80,18);
        c.setBounds(60,40,200,18);
        d.setBounds(60,80,200,18);
        hd.setBounds(90,120,180,18);
        e.setBounds(110,160,60,30);
        f.setBounds(30,160,60,30);
        g.setBounds(190,160,60,30);
        g.addActionListener(new ActionListener() {//对返回按钮添加监听事件
            @SuppressWarnings("deprecation")
            @Override
            public void actionPerformed(ActionEvent arg0) {
                // TODO Auto-generated method stub
                new EnterScreen();

            }
           });
            f.addActionListener(new ActionListener() {//对确认按钮添加监听事件
                @SuppressWarnings("deprecation")
                @Override
                public void actionPerformed(ActionEvent arg0) {
                    // TODO Auto-generated method stub
                    new EnterScreen();

                }
        });
            e.addActionListener(new ActionListener() {//对确认按钮添加监听事件
                @SuppressWarnings("deprecation")
                @Override
                public void actionPerformed(ActionEvent arg0) {
                    // TODO Auto-generated method stub
                    new zhuce();

                }
        });
    }
}

import java.awt.Color;
    import java.awt.Dimension;
    import java.awt.Font;
    import java.awt.FontMetrics;
    import java.awt.Graphics;
    import java.awt.Graphics2D;
    import java.awt.event.MouseEvent;
    import java.awt.event.MouseListener;

    import java.util.Random;

    import javax.swing.JComponent;

    public class Yanzhencode  extends JComponent implements MouseListener {

        private String codes;  //自动生成的验证码

        private int width, height = 40;  //设置验证码高度、宽度

        private int codesLength = 4;  //设置代码长度

        private Random random = new Random(); //生成数字的方法

        public Yanzhencode() {
            width = this.codesLength * 16 + (this.codesLength - 1) * 10; //根据验证码长度设置宽度
            setPreferredSize(new Dimension(width, height));  //设置背景大小
            setSize(width, height);  //设置验证码长度和宽度
            this.addMouseListener(this);
            setToolTipText("点击可更换验证码");
        }
      //得到生成的验证码
        public int getCodesLength() {
            return codesLength;
        }


        //设置验证码的长度
        public void setCodesLength(int codeLength) {
            if(codesLength < 4) {
                this.codesLength = 4;
            } else {
                this.codesLength = codeLength;
            }

        }

        public String getCode() {
            return codes;
        }


           //让验证码产生随机的颜色
        public Color getRandColor(int min, int max) {

            if (min > 255)
                min = 255;
            if (max > 255)
                max = 255;
            int red = random.nextInt(max - min) + min;
            int green = random.nextInt(max - min) + min;
            int blue = random.nextInt(max - min) + min;
            return new Color(red, green, blue);
        }
           // 设置验证码具体的数字或字母是什么
        protected String generateCode() {
            char[] codes = new char[this.codesLength];
            for (int i = 0, len = codes.length; i < len; i++) {
                if (random.nextBoolean()) {
                    codes[i] = (char) (random.nextInt(10) + 48);
                } else {
                    codes[i] = (char) (random.nextInt(26) + 97);
                }
            }
            this.codes = new String(codes);
            return this.codes;
        }


        @Override
        protected void paintComponent(Graphics g) {
            super.paintComponent(g);
            if(this.codes == null || this.codes.length() != this.codesLength) {  //判断生成的验证码是否为空或超出长度
                this.codes = generateCode();
            }
            width = this.codesLength * 16 + (this.codesLength - 1) * 10;
            super.setSize(width, height);  //接口使用，验证码字体大小
            super.setPreferredSize(new Dimension(width, height));//接口使用，验证码背景大小
            Font mFont = new Font("Arial", Font.BOLD | Font.ITALIC, 25);  //设置字体和字体大小
            g.setFont(mFont);  //设置对象
            //绘制出验证码的背景的矩形轮廓
            Graphics2D g2d = (Graphics2D) g;
            g2d.setColor(getRandColor(200, 250));
            g2d.fillRect(0, 0, width, height);
            g2d.setColor(getRandColor(180, 200));
            g2d.drawRect(0, 0, width - 1, height - 1);
            //绘制出验证码背景的线
            int i = 0, len = 150;
            for (; i < len; i++) {
                int x = random.nextInt(width - 1);
                int y = random.nextInt(height - 1);
                int x1 = random.nextInt(width - 10) + 10;
                int y1 = random.nextInt(height - 4) + 4;
                g2d.setColor(getRandColor(180, 200));
                g2d.drawLine(x, y, x1, y1);
            }



            //绘制出验证码的具体字母
            i = 0; len = this.codesLength;
            FontMetrics fm = g2d.getFontMetrics();
            int base = (height - fm.getHeight())/2 + fm.getAscent();
            for(;i<len;i++) {
                int b = random.nextBoolean() ? 1 : -1;
                g2d.rotate(random.nextInt(10)*0.01*b);
                g2d.setColor(getRandColor(20, 130));
                g2d.drawString(codes.charAt(i)+"", 16 * i + 10, base);
            }
        }

        //下一个验证码
        public void nextCode() {
            generateCode();
            repaint();
        }

        @Override
        public void mouseClicked(MouseEvent e) {

            nextCode();
        }

        @Override
        public void mousePressed(MouseEvent e) {
            // TODO Auto-generated method stub

        }

        @Override
        public void mouseReleased(MouseEvent e) {
            // TODO Auto-generated method stub

        }

        @Override
        public void mouseEntered(MouseEvent e) {
            // TODO Auto-generated method stub

        }

        @Override
        public void mouseExited(MouseEvent e) {
            // TODO Auto-generated method stub

        }
    }