验证码

import javax.swing.;
import java.awt.;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.util.Random;

public class CaptchaGUI extends JFrame {

    private JLabel captchaLabel;
    private JTextField inputField;
    private JButton submitButton;
    private String captchaText;

    public CaptchaGUI() {
        setTitle("请输入验证码");
        setSize(400, 200);
        setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        setLocationRelativeTo(null);

        // 创建主面板
        JPanel mainPanel = new JPanel(new BorderLayout());

        // 生成验证码
        captchaText = generateCaptcha();

        // 创建验证码标签
        captchaLabel = new JLabel(captchaText);
        captchaLabel.setFont(new Font("Monospaced", Font.BOLD, 30));
        captchaLabel.setHorizontalAlignment(SwingConstants.CENTER);
        mainPanel.add(captchaLabel, BorderLayout.NORTH);

        // 创建输入框和提交按钮
        JPanel inputPanel = new JPanel(new FlowLayout());
        inputField = new JTextField(10);
        inputPanel.add(inputField);

        submitButton = new JButton("提交");
        submitButton.addActionListener(new ActionListener() {
            @Override
            public void actionPerformed(ActionEvent e) {
                checkCaptcha();
            }
        });
        inputPanel.add(submitButton);

        mainPanel.add(inputPanel, BorderLayout.CENTER);

        // 添加主面板到窗口
        add(mainPanel);
    }

    private String generateCaptcha() {
        String chars = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789";
        Random random = new Random();
        StringBuilder captcha = new StringBuilder();
        for (int i = 0; i < 4; i++) {
            captcha.append(chars.charAt(random.nextInt(chars.length())));
        }
        return captcha.toString();
    }

    private void checkCaptcha() {
        String userInput = inputField.getText();
        if (userInput.equals(captchaText)) {
            JOptionPane.showMessageDialog(this, "验证码正确！");
        } else {
            JOptionPane.showMessageDialog(this, "验证码错误！请重试。");
            captchaText = generateCaptcha();
            captchaLabel.setText(captchaText);
            inputField.setText("");
        }
    }

    public static void main(String[] args) {
        SwingUtilities.invokeLater(new Runnable() {
            @Override
            public void run() {
                new CaptchaGUI().setVisible(true);
            }
        });
    }
}