code: public void isFresh(final String filename, final Handler<Boolean> next) {
          final FileSystem fileSystem = vertx.fileSystem();
  
          fileSystem.props(filename, new AsyncResultHandler<FileProps>() {
              @Override
              public void handle(AsyncResult<FileProps> asyncResult) {
                  if (asyncResult.failed()) {
                      next.handle(false);
                  } else {
                      LRUCache.CacheEntry<String, T> cacheEntry = cache.get(filename);
                      final long lastModified = asyncResult.result().lastModifiedTime();
  
                      if (cacheEntry == null) {
                          next.handle(false);
                      } else {
                          if (cacheEntry.isFresh(lastModified)) {
                              next.handle(true);
                          } else {
                              // not fresh anymore, purge it
                              cache.remove(filename);
                              next.handle(false);
                          }
                      }
                  }
              }
          });
      }
docs: Verifies if a file in the filesystem is still fresh against the cache. Errors are treated as not fresh.
  
  @param filename File to look for
  @param next next asynchronous handler