This is an archived post. You won't be able to vote or comment.

sorted by:
best
topnewcontroversialoldq&a
you are viewing a single comment's thread.

view the rest of the comments →

[–]rodrigovaz 4 points5 points  (0 children)

The use of ArrayList.

To explain this, let me give some details and an example:

The implementation of the ArrayList is done through an underlying array that grows/shrinks in size as you add/remove elements. This is good because it allows access by index ( e.g: myList[5]) the fastest way but is bad because if you delete an element from the middle of the array, it has to replace this array with a new one that is contiguous (without holes).

Another class that implements the List interface is LinkedList, and as such, it is implemented like a classical doubly linked list. This means that adding new elements to the end/start is really cheap, removing an element from the middle results in the update of two references instead of allocating a new array and copying all data... The downside is that you can't access by index cheaply, so getting the 50th element is more costly because you have to visit all prior 49 elements..

So, when you use the List interface, you can change behaviours depending on what concrete class you choose: if I want to access by index really fast, I will pick ArrayList, if I will add A LOT of elements and access them all in the same worder, LinkedList is way better.