private URL[] convertUrlStrsToURLObjs(String[] urlStrs) {
        if (ArrayUtils.isEmpty(urlStrs)) {
            throw new IllegalArgumentException("the arg:urlStrs can not be null or empty");
        }

        URL[] urls;
        try {
            if (ArrayUtils.isEmpty(urlStrs)) {
                throw new IllegalArgumentException("the ctor's param: urlStrs can not be null or empty");
            }

            urls = new URL[urlStrs.length];
            for (int i = 0; i < urlStrs.length; i++) {
                urls[i] = new URL(urlStrs[i]);
            }

        } catch (Exception e) {
            urls = new URL[0];
        }

        return urls;
    }