why can't we use index Of() and contains() methods in arraylist

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Hi all,
Can u please give me valid reasons for why can't we use index Of() and contains() methods in arraylist.

Thanking you,

Posted 14-Oct-11 6:58am

V V S GANGA SUJAN

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Sergey Alexandrovich Kryukov 14-Oct-11 13:41pm

Why do you think we can't?
--SA

V V S GANGA SUJAN 14-Oct-11 14:35pm

Good answer. Thanks alot

Sergey Alexandrovich Kryukov 15-Oct-11 19:51pm

I you think so, please accept it formally (green button) -- thanks.
--SA

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Sergey Alexandrovich Kryukov · Answer 1 · 2011-10-14T07:51:00

Who told you we can't? We can, only this is not the fastest method in the World. For relatively small collections it's perfectly fine. It all depends on your requirements to performance. Also, you should use it with care. See: http://www.daniweb.com/software-development/java/threads/109506[^].

As to the speed of the algorithm, it expect it have the complexity of O(n), that is, linear. (On this notation, see http://en.wikipedia.org/wiki/Big_O_notation[^].) A hash table or a dictionary based on hash values and buckets will give you O(1) — approximating a constant time of execution on big collection, that is, with a big collections the time does not depends on the size of collection. So, IndexOf is only good for small collections or when you want to save on memory and the search time is still acceptable.

—SA