生成随机密码

    /**
     * 生成随机密码
     * @param length
     * @return
     */
    public static String getRandomString(int length) {
        StringBuffer buffer = new StringBuffer("0123456789abcdefghijklmnopqrstuvwxyz");
        StringBuffer sb = new StringBuffer();
        Random r = new Random();
        int range = buffer.length();
        for (int i = 0; i < length; i ++) {
            sb.append(buffer.charAt(r.nextInt(range)));
        }
        return sb.toString();
    }