How is the access time to the last element in an ArrayList determined?

Access time to the last element in an ArrayList in Java is O(1) — constant time. This is because ArrayList is implemented based on an array, and elements are stored in a contiguous block of memory.

To access an element by index, ArrayList simply calculates the address of the element as the base address of the array plus an offset, which takes a fixed amount of time regardless of the size of the list.

Example:

ArrayList<String> list = new ArrayList<>();
list.add("First");
list.add("Second");
String last = list.get(list.size() - 1); // access to the last element in O(1)