SimpleHttpResponse generateCachedResponse(
            final HttpRequest request,
            final HttpCacheEntry entry,
            final Instant now) throws ResourceIOException {
        if (shouldSendNotModifiedResponse(request, entry, now)) {
            return responseGenerator.generateNotModifiedResponse(entry);
        }
        return responseGenerator.generateResponse(request, entry);
    }
Reports the number of times that the cache was able to satisfy
a response by revalidating an existing but stale cache entry.
@return the number of cache revalidations
httpclient5-cache/src/main/java/org/apache/hc/client5/http/impl/cache/CachingExecBase.java