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From "Robert Burrell Donkin (JIRA)" <j...@apache.org>
Subject [jira] Commented: (ECS-1) addElement(Element element) methods can fail
Date Thu, 17 Jul 2008 21:23:31 GMT

    [ https://issues.apache.org/jira/browse/ECS-1?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12614535#action_12614535
] 

Robert Burrell Donkin commented on ECS-1:
-----------------------------------------

Hi Mauro

Sounds good :-)

ECS was created before the unit testing revolution (if you can remember those days) so I'm
going to need a clear head to analyse the patch. Hopefully, should get to before the end of
the weekend.

Thanks for your patience.

Robert

> addElement(Element element) methods can fail
> --------------------------------------------
>
>                 Key: ECS-1
>                 URL: https://issues.apache.org/jira/browse/ECS-1
>             Project: ECS
>          Issue Type: Bug
>         Environment: in Ibm Virtual Machines, but probabily also in Sun Virtual Machines
>            Reporter: Mauro Manfrin
>            Assignee: Robert Burrell Donkin
>            Priority: Critical
>         Attachments: ecs-maintrunk-patches.zip, secondConcreteElement.zip
>
>
> The class ConcreteElement exposes a method
> addElement(Element element)
> that calls
> addElementToRegistry(Integer.toString(element.hashCode()),element);
> so it gives a key valued element.hashCode() to that element.
> That's the point: element.hashCode() can't be a unique key because sometimes we can have
two elements with the same hasocode.
> javadoc states:
> "It is not required that if two objects are unequal according to the 
> equals(java.lang.Object) method, then calling the hashCode method on each of 
> the two objects must produce distinct integer results. However, the 
> programmer should be aware that producing distinct integer results for 
> unequal objects may improve the performance of hashtables."
> So sometimes, two different objects can have the same hashCode!
> So, sometimes two calls to addElement(element) can result in only the second 
> object stored in the ConcreteElement.
> So sometimes, on out instalaltion some table rows misses, or some row cells 
> misses or...

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