code: @Override
      public void close() {
          if (!this.closed.getAndSet(true)) {
              if (this.fileSystem != null) {
                  try {
                      this.fileSystem.close();
                      this.fileSystem = null;
                  } catch (IOException e) {
                      log.warn("Could not close the HDFS filesystem: {}.", e);
                  }
              }
          }
      }
docs: region AutoCloseable Implementation