基于Java随机生成手机短信验证码的实例代码

/**   * 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");  }

/**   * 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;  }