生成八位不重复编码

package com.cw.common.util;

import java.math.BigDecimal;

public class MathUtil {
    public final static char[] BASE={'0','1','2','3','4','5','6','7','8','9',
            'A','B','C','D','E','F','G','H','I','J','K','L','M','N','O','P','Q','R','S','T','U','V','W','X','Y','Z'};

    public static double keepDecimals(double number, int several){
        BigDecimal ra = BigDecimal.valueOf(number);
        return ra.setScale(several, BigDecimal.ROUND_HALF_UP).doubleValue();
    }


    public synchronized static String generateShortCode(Long number, Integer arbitraryBase) {
        StringBuilder result = new StringBuilder();
        if (number == null){
            number = System.currentTimeMillis();
        }
        if (arbitraryBase == null){
            arbitraryBase = 10;
        }
        if (arbitraryBase > BASE.length){
            throw new IndexOutOfBoundsException("超过进制转换限制，最大"+BASE.length);
        }
        //余数
        int remainder = 0;
        //商
        long quotient;
        //当 商 = 0 时结束
        while ((quotient = number / arbitraryBase) != 0){
            //取余
            remainder = (int)(number % arbitraryBase);
            result.insert(0,BASE[remainder]);

            number = quotient;
        }
        //最后取一次余
        remainder = (int)(number % arbitraryBase);
        result.insert(0,BASE[remainder]);

        int length = result.length();
        if (length < 8){
            for (int i = 0; i < (8 - length); i++) {
                result.insert(0,BASE[0]);
            }
        }
        return result.toString();
    }


    /**
     * @Description: 检测是否在误差范围内
     * @param tag   实际值
     * @param tag2 目标值
     * @param range 误差范围
     * @Return java.lang.Boolean
     * @throws
     * 2020/9/8 16:50
     * @Author milk
     */
    public static Boolean withinRange(double tag, double tag2, double range){
        return Math.abs(tag - tag2) <= Math.abs(range);
    }
}