Initialize a collection within an object?

Question

If an object has a property that is a collection, should the object create the collection object or make a consumer check for null? I know the consumer should not assume, just

Answer 1

This depends on the contract you have between your API and the user.

Personally, I like a contract that makes the Object manage its collections, i.e., instantiating them on creation, and ensuring that they can't be set to null via a setter - possibly by providing methods to manage the collection rather than setting the collection itself.

i.e., addFoo(Foo toAdd) instead of setFooSet(Set set), and so on.

But it's up to you.