Question

Ok, so here is my problem:

I have a list containing interfaces – List<Interface> a – and a list of interfaces that extend that interface: List<SubInterface> b. I want to set a = b. I do not wish to use addAll() or anything that will cost more memory as what I am doing is already very cost-intensive. I literally need to be able to say a = b. I have tried List<? extends Interface> a, but then I cannot add Interfaces to the list a, only the SubInterfaces. Any suggestions?

I want to be able to do something like this:

List<SubRecord> records = new ArrayList<SubRecord>();
//add things to records
recordKeeper.myList = records;

The class RecordKeeper is the one that contains the list of Interfaces (NOT subInterfaces)

public class RecordKeeper{
    public List<Record> myList;
}

Answer 1

So, the rather simple solution a friend of mine found was this:

recordKeeper.myList = (List<Record>)(List<? extends Record>)records;

This works as I understand it because it takes baby steps. List<SubRecord> is a List<? extends Record>, and List<? extends Record> is a List<Record>. It might not be pretty, but it works nonetheless.