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From "Robert Burrell Donkin (JIRA)" <j...@apache.org>
Subject [jira] Closed: (ECS-1) addElement(Element element) methods can fail
Date Sun, 27 Jul 2008 11:32:32 GMT

     [ https://issues.apache.org/jira/browse/ECS-1?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
]

Robert Burrell Donkin closed ECS-1.
-----------------------------------

    Resolution: Fixed

Committed. Many Thanks.

Please test and reopen if it hasn't be applied cleanly. (The diffs didn't apply cleanly against
trunk, most likely due to formatting issues.)

Apologies for my slowness and thanks again for taking the trouble to report and fix this issue.

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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