LinkedList vs ArrayList on a specific android example [duplicate]

Question

I return a List from my A class. I would like to remove the first element from the list and add it as the last element to the same list. I did it this way.

myList.add(myList.get(0));
myList.remove(0);

The target hardware is Android OS. Should I code my A class in a way that it returns an ArrayList, or a LinkedList? Which would be better for the following scenarios:

1. myList has always 100 elements

2. myList has always 10 elements

Maybe I see a problem where there is none. Do you think I shouldn't care for performance in this case, since the problem size is (for both 1 and 2) is small?

I am aware of the saying "premature optimisation is the root of all evil". That's why I am hesitating before changing my implemantation (as for now, my A object returns an ArrayList).

Answer 1

Short answer you should go for LinkedList if you are adding/removing/updating element frequently, especially for the case of first/last elements, as it contains a pointer to the first and last node

Long answer LinkedList add method gives O(1) performance while ArrayList gives O(n) in the worst case. LinkedList is faster. It will just reference the nodes so the first one disappears:


In addition, ArrayList is good for write-once-read-many or appenders, but bad at add/remove from the front or middle.

For instance, removing an element from a linked list costs O(1), while doing so for an array (array list) costs O(n).

But, this is not always a rule, as bigoh post states:

Big-oh notation can give very good ideas about performance for large amounts of data, but the only real way to know for sure is to actually try it with large data sets. There may be performance issues that are not taken into account by big-oh notation, eg, the effect on paging as virtual memory usage grows. Although benchmarks are better, they aren't feasible during the design process, so Big-Oh complexity analysis is the choice.

The above is validated with this post, where LinkedList also proved slow.

Finally, for further/future reference, please take a look at the use case comparison of them, according to javaconceptoftheday.com:

References
http://docs.oracle.com/javase/8/docs/api/java/util/LinkedList.html http://docs.oracle.com/javase/8/docs/api/java/util/ArrayList.html