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https://issues.apache.org/jira/browse/FTPSERVER-375?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13051716#comment-13051716
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Niklas Gustavsson commented on FTPSERVER-375:
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> However, equals() and hashCode() are not calculated simulataneously, so if
> the external conditions change between calling the two methods,
> they may disagree.
>
> Further, a hashCode should not change if the object does not change (and
> should not change at all if used in some kinds of map).
>
> It would be safer to fetch the canonical path once, and base the methods on
> that.
I still think this discussion is getting a bit theoretical for this particular
case, but I'll bite. As far as I know, the hashCode() contract says that it
might change, if the result of equals changes. Since, in some file systems, the
canonical path might change when the file is changed (created/deleted), both
equals and hashCode might the change. From our usage, this seems reasonable.
From the Javadoc: "Whenever it is invoked on the same object more than once
during an execution of a Java application, the hashCode method must
consistently return the same integer, provided no information used in equals
comparisons on the object is modified"
And again, yes, the equals method is needed. It is for example used in RMD to
ensure that we do not delete the cwd.
I would be happy to add documentation to specify the contract in
FtpFile.equals(), feel free to open an issue for this.
> [FindBugs] NativeFtpFile implements equals(), but does not - hashCode()
> -----------------------------------------------------------------------
>
> Key: FTPSERVER-375
> URL: https://issues.apache.org/jira/browse/FTPSERVER-375
> Project: FtpServer
> Issue Type: Wish
> Components: Core
> Reporter: Sergey Vladimirov
> Priority: Minor
> Labels: equality, findbugs
> Fix For: 1.0.6, 1.1.0
>
>
> In fact, i can't find why it need to implement equals() in first place. If
> for any map - then hashCode() will also be required. For example,
> this.file.getCanonicalFile().hashCode()
> Anyway, could we please have a comment why do we need equals() method? :)
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