[Java] 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;
  }