private static <V> ListenableFuture<V> closedChannelFuture() {
    SettableFuture<V> future = SettableFuture.create();
    future.setException(new ClosedChannelException());
    return future;
  }
Immediate future indicating that the channel is closed.
jimfs/src/main/java/com/google/common/jimfs/JimfsAsynchronousFileChannel.java