@Override
  public MappedByteBuffer map(MapMode mode, long position, long size) throws IOException {
    // would like this to pretend to work, but can't create an implementation of MappedByteBuffer
    // well, a direct buffer could be cast to MappedByteBuffer, but it couldn't work in general
    throw new UnsupportedOperationException();
  }
Ends a blocking operation, throwing an exception if the thread was interrupted while blocking
or if the channel was closed from another thread.
jimfs/src/main/java/com/google/common/jimfs/JimfsFileChannel.java