public static String appendStyles(final String existing, final String... styles) {
        String str = NullSafe.string(existing).trim();
        if (styles != null && styles.length > 0) {
            if (!str.isEmpty()) {
                str += " ";
            }
            str = str + NullSafe.stream(styles)
                    .map(String::trim)
                    .collect(Collectors.joining(" "));
        }
        return str;
    }
Util class for doing various things not emulated in GWT
stroom-util-shared/src/main/java/stroom/util/shared/GwtUtil.java