Java serialization: readObject() vs. readResolve()

Question

The book Effective Java and other sources provide a pretty good explanation on how and when to use the readObject() method when working with serializable Java class

Answer 1

readResolve is for when you may need to return an existing object, e.g. because you're checking for duplicate inputs that should be merged, or (e.g. in eventually-consistent distributed systems) because it's an update that may arrive before you're aware of any older versions.