准备运营的卡号生成办法

import java.util.HashMap;
import java.util.Map;
import java.util.Random;
 
/**
 * 序列号生成器
 * @author Johney
 *
 */
public class SerialNumberUtil {
    /**自定义进制(0,1没有加入,容易与o,l混淆)*/
    private static final char[] r = new char[] { \'Q\', \'w\', \'E\', \'8\', \'a\', \'S\', \'2\', \'d\', \'Z\', \'x\', \'9\', \'c\', \'7\', \'p\', \'O\', \'5\', \'i\', \'K\', \'3\', \'m\', \'j\', \'U\', \'f\', \'r\', \'4\', \'V\', \'y\', \'L\', \'t\', \'N\', \'6\', \'b\', \'g\', \'H\' };
    /**自动补全组(不能与自定义进制有重复)*/
    private static final char[] b = new char[] {  \'e\', \'A\', \'q\', \'W\',\'s\', \'D\', \'z\', \'X\', \'C\',\'I\', \'k\', \'P\', \'o\',  \'M\', \'J\', \'u\', \'F\', \'R\', \'v\', \'Y\', \'T\', \'n\', \'B\', \'G\', \'h\' };
    /**进制长度*/
    private static final int l = r.length;
    /**序列最小长度*/
    private static final int s = 8;
 
    /**
      * 根据ID生成六位随机码
      * @param num ID
      * @return 随机码
      */
    public static String toSerialNumber(long num) {
        char[] buf = new char[32];
        int charPos = 32;
 
        while ((num / l) > 0) {
            buf[--charPos] = r[(int) (num % l)];
            num /= l;
        }
        buf[--charPos] = r[(int) (num % l)];
        String str = new String(buf, charPos, (32 - charPos));
        //不够长度的自动随机补全
        if (str.length() < s) {
            StringBuffer sb = new StringBuffer();
            Random rnd = new Random();
            for (int i = 0; i < s - str.length(); i++) {
                sb.append(b[rnd.nextInt(24)]);
            }
            str += sb.toString();
        }
        return str;
    }
    public static void main(String[] args) 
    { 
      Map<String,String> map = new HashMap<String,String>();
      
      for(int i=0;i<10000000;i++)
      {
            String a=SerialNumberUtil.toSerialNumber(i);
            map.put(String.valueOf(i),a);             
      }
      //经验证，10的7次方时，无重复，可使用。
      System.out.println(map.size());    
    }
}