import java.awt.Color;import java.awt.Font;import java.awt.Graphics;import java.awt.image.BufferedImage;import java.io.ByteArrayInputStream;import java.io.ByteArrayOutputStream;import java.util.Random;import javax.imageio.ImageIO;import javax.imageio.stream.ImageOutputStream;public class RandomNumUtil {    private ByteArrayInputStream image;//图像       private String str;//验证码              private RandomNumUtil(){           init();//初始化属性       }            public static RandomNumUtil Instance(){           return new RandomNumUtil();       }            public ByteArrayInputStream getImage(){           return this.image;       }            public String getString(){           return this.str;       }              private void init() {           //       在内存中创建图象           int width=85, height=20;           BufferedImage image = new BufferedImage(width, height, BufferedImage.TYPE_INT_RGB);           //       获取图形上下文           Graphics g = image.getGraphics();           //      生成随机类           Random random = new Random();           //       设定背景色           g.setColor(getRandColor(200,250));           g.fillRect(0, 0, width, height);           //      设定字体           g.setFont(new Font("Times New Roman",Font.PLAIN,18));           //       随机产生155条干扰线，使图象中的认证码不易被其它程序探测到           g.setColor(getRandColor(160,200));           for (int i=0;i<155;i++)           {            int x = random.nextInt(width);            int y = random.nextInt(height);                   int xl = random.nextInt(12);                   int yl = random.nextInt(12);            g.drawLine(x,y,x+xl,y+yl);           }           //       取随机产生的认证码(6位数字)          String sRand="";        for (int i=0;i<6;i++){               String rand=String.valueOf(random.nextInt(10));               sRand+=rand;                 // 将认证码显示到图象中               g.setColor(new Color(20+random.nextInt(110),20+random.nextInt(110),20+random.nextInt(110)));               //      调用函数出来的颜色相同，可能是因为种子太接近，所以只能直接生成               g.drawString(rand,13*i+6,16);        }        //赋值验证码        this.str=sRand;                 //图象生效           g.dispose();           ByteArrayInputStream input=null;           ByteArrayOutputStream output = new ByteArrayOutputStream();           try{               ImageOutputStream imageOut = ImageIO.createImageOutputStream(output);               ImageIO.write(image, "JPEG", imageOut);               imageOut.close();               input = new ByteArrayInputStream(output.toByteArray());           }catch(Exception e){               System.out.println("验证码图片产生出现错误："+e.toString());           }                      this.image=input;     }            private Color getRandColor(int fc,int bc){           Random random = new Random();           if(fc>255) fc=255;           if(bc>255) bc=255;           int r=fc+random.nextInt(bc-fc);           int g=fc+random.nextInt(bc-fc);           int b=fc+random.nextInt(bc-fc);           return new Color(r,g,b);      }}