Invitation code generator Java code

Invitation code generator, which can reversely calculate the user ID based on the invitation code

import java.util.Random;
 
/**
 * 邀请码生成器，算法原理：<br/>
 * 1) 获取id: 1127738 <br/>
 * 2) 使用自定义进制转为：gpm6 <br/>
 * 3) 转为字符串，并在后面加&#39;o&#39;字符：gpm6o <br/>
 * 4）在后面随机产生若干个随机数字字符：gpm6o7 <br/>
 * 转为自定义进制后就不会出现o这个字符，然后在后面加个&#39;o&#39;，这样就能确定唯一性。最后在后面产生一些随机字符进行补全。<br/>
 * @author jiayu.qiu
 */
public class ShareCodeUtil {
 
    /** 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[]{&#39;q&#39;, &#39;w&#39;, &#39;e&#39;, &#39;8&#39;, &#39;a&#39;, &#39;s&#39;, &#39;2&#39;, &#39;d&#39;, &#39;z&#39;, &#39;x&#39;, &#39;9&#39;, &#39;c&#39;, &#39;7&#39;, &#39;p&#39;, &#39;5&#39;, &#39;i&#39;, &#39;k&#39;, &#39;3&#39;, &#39;m&#39;, &#39;j&#39;, &#39;u&#39;, &#39;f&#39;, &#39;r&#39;, &#39;4&#39;, &#39;v&#39;, &#39;y&#39;, &#39;l&#39;, &#39;t&#39;, &#39;n&#39;, &#39;6&#39;, &#39;b&#39;, &#39;g&#39;, &#39;h&#39;};
 
    /** (不能与自定义进制有重复) */
    private static final char b=&#39;o&#39;;
 
    /** 进制长度 */
    private static final int binLen=r.length;
 
    /** 序列最小长度 */
    private static final int s=6;
 
    /**
     * 根据ID生成六位随机码
     * @param id ID
     * @return 随机码
     */
    public static String toSerialCode(long id) {
        char[] buf=new char[32];
        int charPos=32;
 
        while((id / binLen) > 0) {
            int ind=(int)(id % binLen);
            // System.out.println(num + "-->" + ind);
            buf[--charPos]=r[ind];
            id /= binLen;
        }
        buf[--charPos]=r[(int)(id % binLen)];
        // System.out.println(num + "-->" + num % binLen);
        String str=new String(buf, charPos, (32 - charPos));
        // 不够长度的自动随机补全
        if(str.length() < s) {
            StringBuilder sb=new StringBuilder();
            sb.append(b);
            Random rnd=new Random();
            for(int i=1; i < s - str.length(); i++) {
            sb.append(r[rnd.nextInt(binLen)]);
            }
            str+=sb.toString();
        }
        return str;
    }
 
    public static long codeToId(String code) {
        char chs[]=code.toCharArray();
        long res=0L;
        for(int i=0; i < chs.length; i++) {
            int ind=0;
            for(int j=0; j < binLen; j++) {
                if(chs[i] == r[j]) {
                    ind=j;
                    break;
                }
            }
            if(chs[i] == b) {
                break;
            }
            if(i > 0) {
                res=res * binLen + ind;
            } else {
                res=ind;
            }
            // System.out.println(ind + "-->" + res);
        }
        return res;
    }
}