private static OptionalLong parse(final String string) {
        try {
            if (NullSafe.isNonBlankString(string)) {
                // Parse numeric part of dir name.
                return OptionalLong.of(Long.parseLong(string));
            } else {
                return OptionalLong.empty();
            }
        } catch (final NumberFormatException e) {
            return OptionalLong.empty();
        }
    }
Extract the number represented by the supplied `0` padded string.

@param string A directory name.
@return The long part of the string if found, else empty.
stroom-proxy/stroom-proxy-app/src/main/java/stroom/proxy/app/handler/NumberedDirProvider.java