java实现生成带颜色的4位随机验证码完整代码

好的，以下是完整的 Java 代码实现生成带颜色的4位随机验证码：

import java.awt.Color;
import java.awt.Font;
import java.awt.Graphics2D;
import java.awt.image.BufferedImage;
import java.util.Random;

import javax.imageio.ImageIO;

import java.io.File;
import java.io.IOException;

public class CaptchaGenerator {
    private static final int WIDTH = 80; // 验证码图片宽度
    private static final int HEIGHT = 30; // 验证码图片高度
    private static final int CODE_LENGTH = 4; // 验证码长度
    private static final String CODE_CHARACTERS = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789"; // 验证码字符集

    public static void main(String[] args) {
        BufferedImage image = generateCaptcha();
        try {
            ImageIO.write(image, "PNG", new File("captcha.png")); // 保存验证码到文件
            System.out.println("验证码已生成并保存到文件。");
        } catch (IOException e) {
            e.printStackTrace();
        }
    }

    public static BufferedImage generateCaptcha() {
        BufferedImage image = new BufferedImage(WIDTH, HEIGHT, BufferedImage.TYPE_INT_RGB);
        Graphics2D g = (Graphics2D) image.getGraphics();
        Random random = new Random();

        // 生成随机颜色的背景
        g.setColor(new Color(random.nextInt(256), random.nextInt(256), random.nextInt(256)));
        g.fillRect(0, 0, WIDTH, HEIGHT);

        // 生成验证码
        StringBuilder code = new StringBuilder();
        for (int i = 0; i < CODE_LENGTH; i++) {
            char c = CODE_CHARACTERS.charAt(random.nextInt(CODE_CHARACTERS.length()));
            code.append(c);
            g.setColor(new Color(random.nextInt(256), random.nextInt(256), random.nextInt(256)));
            g.setFont(new Font(Font.SANS_SERIF, Font.BOLD, 20));
            g.drawString(String.valueOf(c), 15 + i * 15, 20);
        }

        // 添加干扰线
        for (int i = 0; i < 5; i++) {
            g.setColor(new Color(random.nextInt(256), random.nextInt(256), random.nextInt(256)));
            int x1 = random.nextInt(WIDTH);
            int y1 = random.nextInt(HEIGHT);
            int x2 = random.nextInt(WIDTH);
            int y2 = random.nextInt(HEIGHT);
            g.drawLine(x1, y1, x2, y2);
        }

        g.dispose();
        return image;
    }
}

该代码会在当前目录下生成一个名为 `captcha.png` 的验证码图片文件。你可以使用其他文件格式，如 JPG、GIF 等，只需要将 `ImageIO.write()` 方法的第二个参数改为对应的文件格式即可。