记录随机数几种方法，自用

1 public static String generateString(int length) // 参数为返回随机数的长度
2     {
3         StringBuffer sb = new StringBuffer();
4         Random random = new Random();
5         for (int i = 0; i < length; i++) {
6             sb.append(numberChar.charAt(random.nextInt(numberChar.length())));
7         }
8         return sb.toString();
9     }