@Nullable T read()
If there will be many calls to
read() for different state in short succession, you
should first call
readLater() for all of them so the reads can potentially be batched
(depending on the underlying implementation}.
The returned object should be independent of the underlying state. Any direct modification of the returned object should not modify state without going through the appropriate state interface, and modification to the state should not be mirrored in the returned object.