code: @Override
      public void close() {
          if (!this.closed.get()) {
              ArrayList<RocksDBCache> toClose;
              synchronized (this.caches) {
                  toClose = new ArrayList<>(this.caches.values());
              }
  
              toClose.forEach(RocksDBCache::close);
              this.closed.set(true);
              log.info("{}: Closed.", LOG_ID);
          }
      }
docs: region AutoCloseable Implementation