java如何生成imagecode？？？？？

package image;import java.awt.Color;import java.awt.Graphics;import java.awt.image.BufferedImage;import java.io.File;import java.io.IOException;import java.util.Random;import javax.imageio.ImageIO;public class ImageCode {	public static void main(String[] args) throws IOException {		generateImageCode();	}		public static void generateImageCode() throws IOException {		System.out.println("generating image code...");				int height = 22;		int width = 68;		// 1.创建图片缓存区		BufferedImage image = new BufferedImage(width, height, BufferedImage.TYPE_INT_RGB);				// 2.创建绘制环境		Graphics paint = image.getGraphics();		Color c = new Color(200, 150, 255);		// 设置画笔		paint.setColor(c);		// 画背景		paint.fillRect(0, 0, width, height);				// 绘制数字和字母		StringBuffer codes = new StringBuffer();		char[] ch = "QWERTYUIOPASDFGHJKLZXCVBNM1234567890".toCharArray();		Random r = new Random();		int index;				for(int i = 0; i < 4; i++) {			index = r.nextInt(ch.length);			// 设置文本颜色			paint.setColor(new Color(r.nextInt(88), r.nextInt(150), r.nextInt(255)));			paint.drawString(ch[index]+"", (i*16)+3, 18);			codes.append(ch[index]);		}				File file = new File("./out.jpg");		ImageIO.write(image, "JPG", file);				System.out.println("generate image code successfully");	}}