Java随机生成手机短信验证码

简单版

     /**
     * 产生4位随机数(0000-9999)
     *
     * @return 4位随机数
     */
    public static String getFourRandom() {
        return StringUtils.leftPad(new Random().nextInt(10000) + "", 4, "0");
    }

复杂版

     /**
     * 创建指定数量的随机字符串
     * @param numberFlag 是否是数字
     * @param length
     * @return
     */
    public static String createRandom(boolean numberFlag, int length){
        String retStr = "";
        String strTable = numberFlag ? "1234567890" : "1234567890abcdefghijkmnpqrstuvwxyz";
        int len = strTable.length();
        boolean bDone = true;
        do {
            retStr = "";
            int count = 0;
            for (int i = 0; i < length; i++) {
                double dblR = Math.random() * len;
                int intR = (int) Math.floor(dblR);
                char c = strTable.charAt(intR);
                if (('0' <= c) && (c <= '9')) {
                    count++;
                }
                retStr += strTable.charAt(intR);
            }
            if (count >= 2) {
                bDone = false;
            }
        } while (bDone);

        return retStr;
    }