写一段java生成验证码的代码案例

Sure! 以下是一段使用Java生成验证码的代码案例：

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

public class CaptchaGenerator {
  private static final int WIDTH = 120;
  private static final int HEIGHT = 40;
  private static final String CHARACTERS = "ABCDEFGHJKLMNPQRSTUVWXYZ23456789";
  private static final int CHARACTERS_LENGTH = CHARACTERS.length();
  
  public static String generateCaptcha() {
    BufferedImage image = new BufferedImage(WIDTH, HEIGHT, BufferedImage.TYPE_INT_RGB);
    Graphics graphics = image.getGraphics();
    
    Random random = new Random();
    
    // Set background color
    graphics.setColor(Color.WHITE);
    graphics.fillRect(0, 0, WIDTH, HEIGHT);
    
    // Draw random characters
    StringBuilder captcha = new StringBuilder();
    for (int i = 0; i < 6; i++) {
      char ch = CHARACTERS.charAt(random.nextInt(CHARACTERS_LENGTH));
      captcha.append(ch);
      
      int x = 10 + (i * 18);
      int y = 18 + random.nextInt(10);
      graphics.setColor(new Color(random.nextInt(200), random.nextInt(200), random.nextInt(200)));
      graphics.setFont(new Font("Arial", Font.BOLD, 20));
      graphics.drawString(Character.toString(ch), x, y);
    }
    
    // Draw random lines
    for (int i = 0; i < 5; i++) {
      int x1 = random.nextInt(WIDTH);
      int y1 = random.nextInt(HEIGHT);
      int x2 = random.nextInt(WIDTH);
      int y2 = random.nextInt(HEIGHT);
      graphics.setColor(new Color(random.nextInt(200), random.nextInt(200), random.nextInt(200)));
      graphics.drawLine(x1, y1, x2, y2);
    }
    
    return captcha.toString();
  }
}

以上就是生成验证码的Java代码案例。如果你对这个问题有更多疑问或者需要帮助，请随时告诉我。