java生成随机数

private static final String CODE = "0123456789";

    /**
     * 生成随机字符，不含0和O，字符全为大写
     * 
     * @param length
     * @return
     */
    public static String getCaptachCode(int length) {
        String str = "";
        for (int i = 0; i < length; i++) {
            str = str + CODE.charAt((int) (CODE.length() * java.lang.Math.random()));
        }
        return str;
    }