@Override
    public long contentLength() {
        final Long contentLength = (Long) cache.get(HttpHeaderNames.CONTENT_LENGTH);
        if (contentLength != null) {
            return contentLength;
        }

        final String contentLengthString = get(HttpHeaderNames.CONTENT_LENGTH);
        if (contentLengthString != null) {
            final long parsed = Long.parseLong(contentLengthString);
            cache.put(HttpHeaderNames.CONTENT_LENGTH, parsed);
            return parsed;
        } else {
            cache.put(HttpHeaderNames.CONTENT_LENGTH, -1L);
            return -1L;
        }
    }
Adds the specified {@code setCookies} with {@link HttpHeaderNames#SET_COOKIE}.
core/src/main/java/com/linecorp/armeria/common/HttpHeadersBase.java