*         .onlyIfCached()
 *         .build())
 *     .url("http://publicobject.com/helloworld.txt")
 *     .build();
 * Response forceCacheResponse = client.newCall(request).execute();
 * if (forceCacheResponse.code() != 504) {
 *   // The resource was cached! Show it.
 * } else {
 *   // The resource was not cached.
 * }
 * ```
 *
 * This technique works even better in situations where a stale response is better than no response.