Different between immutable and effectively immutable objects?

Question

This is a sentence from Java Concurrency in Practice

Shared read-only objects include immutable and effectively immutable objects.

Answer 1

Take a look at this answer:

effectively immutable and immutable The difference between effectively immutable and immutable is that in the first case you still need to publish the objects in a safe way. For the truly immutable objects that isn't needed. So truly immutable objects are preferred because they are easier to publish, the reasons I stated above say why you might prefer unsynchronized publication.

https://stackoverflow.com/a/7887675/1007546