生产随机字符串

public static String createStringCode(boolean numberFlag, int length) {
    String retStr = "";
    String strTable = numberFlag ? "1234567890" : "1234567890abcdefghijkmnpqrstuvwxyz";
    int len = strTable.length();
    retStr = "";
    for (int i = 0; i < length; i++) {
        double v = Math.random() * len;
        logger.info(v+"------");
        retStr += strTable.charAt((int)Math.floor(v));
    }
    return retStr;
}