That isn't overloading. They both have the signature
saveList(List). Remember that generic information is removed at runtime, so the compiler cannot distinguish those two methods.
I am not sure what the correct answer is because you haven't provided enough information about the two methods. I am a bit suspicious, however, that you are acting outwith the List's original owning object, which means you are breaching the single responsibility principle. I have found a few places where you can find out about that:
1 2 and enclosed links. If there is an object with those Lists in, maybe that object should be responsible for maintaining those Lists. Unless you have a generic list saving utility, consider moving those methods elsewhere.