Java setting private fields inside constructors

Question

Common design practice is to make instance variables private and have public getters and setters to access them. But many times I have seen code samples on the internet that

Answer 1

My preferred approach (as described by Joshua Bloch in "Effective Java") is to make the constructor private, make the fields final (i.e., eliminate the setters entirely), and require clients to obtain instances either using the Builder Pattern or Factory Method Pattern, which would take care of any necessary validation to protect invariants. Then the (private) constructor would simply directly assign the given parameters (which have already been validated by the Builder or Factory Method) to the appropriate fields, which are private and final.