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From "Andrei Iliev (JIRA)" <j...@apache.org>
Subject [jira] Commented: (LUCENENET-292) Optimization of EquatableList<T>
Date Fri, 20 Nov 2009 15:28:40 GMT

    [ https://issues.apache.org/jira/browse/LUCENENET-292?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12780596#action_12780596
] 

Andrei Iliev commented on LUCENENET-292:
----------------------------------------

EquatableList<T> supposed to be replacement of Java ArrayList. In the current implementation
it is not.  EquatableList<T>  should not override == (!=)operators.  In java,   operator
== compares references but  not values. Example in java:
ArrayList list = new ArrayList();
        list.add(1);
        list.add(2);
        list.add(3);
        ArrayList list2 = (ArrayList)list.clone();
        System.out.println("Equals:"+list2.equals(list)); // will print true
        System.out.println("=="+(list2 == list));  // will print false



> Optimization of EquatableList<T>
> --------------------------------
>
>                 Key: LUCENENET-292
>                 URL: https://issues.apache.org/jira/browse/LUCENENET-292
>             Project: Lucene.Net
>          Issue Type: Improvement
>            Reporter: Nicholas Paldino
>            Priority: Minor
>         Attachments: SupportClass.patch
>
>
> When comparing two IEnumerable<T> implementations, a shortcut can be taken to check
to see if both IEnumerable<T> expose operations which returns a count of items (sequences
cannot be equal if the number of elements in the sequences are not equal).
> Typically, in .NET, this is expressed through the implementation of the ICollection or
ICollection<T> interface.
> Before enumerating through each element and comparing the two for equality, if the counts
are accessible, they should be compared to see if the number of elements in the two sequences
are equal.  If a comparison is able to be made before enumerating, it will be much more performant
for comparisons of sequences where each is ~N, but both are not equal to N, and N is very
large.
> Patch to follow.

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