If the list contains n elements, the Big-O of operations is as follows:
| Method | ArrayList | LinkedList |
| get, set ith | O(1) | O(n) |
| ... at front or end | O(1) | O(1) |
| add, remove ith | O(n) | O(n) |
| ... at front | O(n) | O(1) |
| ... at end | O(1) | O(1) |
| ... in ListIterator | O(n) | O(1) |
| contains | O(n) | O(n) |
To choose the best Collection, you need to understand which methods you will use and how often you use them.
If an O(n) method is used within a loop up to n, the total time required is O(n2) even though the code may look like it is O(n). Thus, library methods can be a Big-O trap for the unwary.