@Override
    public boolean isEmpty() {
        return super.isEmpty() && !cachePublic && !cachePrivate && !immutable &&
               !mustRevalidate && !proxyRevalidate && sMaxAgeSeconds < 0;
    }
Returns a newly created {@link ServerCacheControlBuilder} with all directives disabled initially.
core/src/main/java/com/linecorp/armeria/common/ServerCacheControl.java