Will I be able to successfully deserialize a previous version of my class?

Question

I have a class like this

class MyClass implements MyInterface, Serializable {
private static final serialVersionUID = 42;
...
}

interface MyInterface {
void A();
void B();
}

I have saved in a database some serialized instances of MyClass.

Now, I'm adding a new function to MyInterface so it becomes:

interface MyInterface {
void A();
void B();
void C();
}

And I have implemented C() in MyClass.

Will my previously serialized instances deserialize as the new class with no problem? I think yes but wanted to confirm, if possible, with explanation.

Answer 1

Yes, there should be no problems with adding a new function, so long as the serialVersionUID stays the same, as Java only keeps information about fields when serializing an object.

From ObjectOutputStream:

State [of the serialized object] is saved by writing the individual fields to the ObjectOutputStream using the writeObject method…

Answer 2

If serialVersionUID is the same in the modified class serialization will try to do its best to deserialize data into the new class ignoring any differences.