Why is .add(i, E) big O(n) in Java ArrayList?

Question

I'm wondering why exactly .add(i, E) is O(n) when .get(i) is O(1)? Is it because potentially n elements must be shifted over to the right after the insertion?

Answer 1

remember Big O notation shows the Order of magnitude of the problem not its best case solution... so yes shifting the other elements in the ArrayList (backed by an Array as Siddhartha mentions) is what causes it to be O(n).