Better design in Java application

Trying to see better design for the following. Not familiar with design patterns but trying to see if any design pattern or otherwise will make better solution.

Consider
Class A {
String field1;
String field2;
CA ca;
}

Class B {
String bfield1;
String field2;
Common cb;
}

Class C {
String cfield1;
String cfield2;
Common cc;
additional fields etc..
}

Do some process and based on some criteria
Create - Populate Object C from fields from A; NotActive - Populate Object C from fields of B but need to apply rules to cb before mapping to cc; Update - Compare fields from A and B and also apply rules to ca and cb then populate Object C.

One way is to use visitor pattern for create, notactive,update that returns the mapped Class C object. The other way of looking is since class B is more similar to Class C, for non active and update use similar process for mapping. I think I need to address a) Which design will help in mapping between classes without rewriting the code in several places. b) Where to apply rules for the ca,cb and cc. Do I give the responsibility to Class A, Class B and Class C

Appreciate any help.