class CommonUtils {

    public static String join(Collection collection, String separator) {
        if (isEmpty(collection)) {
            return StringUtils.EMPTY;
        }
        StringBuilder sb = new StringBuilder();
        for (Object object : collection) {
            if (object != null) {
                String string = StringUtils.toString(object);
                if (string != null) {
                    sb.append(string).append(separator);
                }
            }
        }
        return sb.length() > 0 ? sb.substring(0, sb.length() - separator.length()) : StringUtils.EMPTY;
    }

}