[jira] [Comment Edited] (OFBIZ-6298) Java collection use optimized

["Nicolas Malin (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/OFBIZ-6298?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14510624#comment-14510624 ] 

Nicolas Malin edited comment on OFBIZ-6298 at 4/24/15 8:17 AM:
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{quote} 
[~deepak.dixit] : We should use the LinkedHashMap for controller pre/post processor eventLists (ConfigXMLReader.java:180) as HashMap does not maintain the iteration order. 
{quote}


was (Author: soledad):
{quote} 
[~deepak] : We should use the LinkedHashMap for controller pre/post processor eventLists (ConfigXMLReader.java:180) as HashMap does not maintain the iteration order. 
{quote}

> Java collection use optimized
> -----------------------------
>
>                 Key: OFBIZ-6298
>                 URL: https://issues.apache.org/jira/browse/OFBIZ-6298
>             Project: OFBiz
>          Issue Type: Improvement
>          Components: ALL COMPONENTS
>    Affects Versions: Trunk
>            Reporter: Nicolas Malin
>            Assignee: Nicolas Malin
>            Priority: Minor
>              Labels: collection, performance
>
> With the javolution collection cleaning (OFBIZ-5169,OFBIZ-5781) , we need to realize a second pass to control what instantiation would be better.
> For List between LinkedList, ArrayList
> {quote}
> Using ArrayList, rather than LinkedList, as a default is a good approach because ArrayList will work better in most situations (in terms of algorithmic runtimes and memory footprints).
> However I think it is important to wisely choose ArrayList or LinkedList based on the context, because sometimes a linked list may be a better choice: I am not saying we should do it now and we can tackle this at a later moment, possibly focusing only on list that can be very big and analyzing their usage to see if array or linked list is better; it would be also nice, when we use ArrayList, to see if we can predict the capacity of the list and allocate it at creation: if we can do this we will have a more predictable memory usage and less unpredictable peaks under heavy load (when the array capacity is reached and the array is copied to a new one with double capacity).
> {quote}
> more documentation on :
>  * https://docs.oracle.com/javase/tutorial/collections/implementations/list.html
>  * http://stackoverflow.com/questions/322715/when-to-use-linkedlist-over-arraylist
> For Map between HashMap and LinkedHashMap :
> {quote}
> Javolution Map Iterators return items in insertion sequence (HashMap does not), so any code relying on the original insertion order must use a LinkedHashMap.
> {quote}
>  * http://stackoverflow.com/questions/2889777/difference-between-hashmap-linkedhashmap-and-treemap
> If you detect an optimization, please comments this issues



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