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https://issues.apache.org/jira/browse/PDFBOX-1512?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13939639#comment-13939639
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John Hewson commented on PDFBOX-1512:
-------------------------------------
{quote}
Some algorithms don't care, which may result in inconsistent ordering across
multiple calls
{quote}
I don't see how this would happen unless the algorithm was randomised. For a
given input the output should always be the same, regardless.
But as you say the ordering is not sufficiently defined, so there may be more
than one sort which allowed. Perhaps we need some more sophisticated rule for
determining reading order? Perhaps [Topological
sorting|http://en.wikipedia.org/wiki/Topological_sorting] may be of relevance?
> TextPositionComparator is not compatible with Java 7
> ----------------------------------------------------
>
> Key: PDFBOX-1512
> URL: https://issues.apache.org/jira/browse/PDFBOX-1512
> Project: PDFBox
> Issue Type: Bug
> Components: Text extraction
> Affects Versions: 1.7.1
> Environment: Java 7
> Reporter: Benjamin Papez
> Assignee: Andreas Lehmkühler
> Attachments: FOP-2252.pdf, TextPositionComparator.java,
> WFI_PDFParser_TextPostionComparator.txt, immo-kurier_arsenal_93x62.pdf
>
>
> The TextPostionCompartor causes the following exception running on Java 7:
> Unexpected RuntimeException from
> org.apache.tika.parser.ParserDecorator$1@9007fa2 Original cause: Comparison
> method violates its general contract!
> I think the problem is with this check:
> if ( yDifference < .1 ||
> (pos2YBottom >= pos1YTop && pos2YBottom <= pos1YBottom) ||
> (pos1YBottom >= pos2YTop && pos1YBottom <= pos2YBottom))
> as it violates the contract requirement:
> The implementor must also ensure that the relation is transitive:
> ((compare(x, y)>0) && (compare(y, z)>0)) implies compare(x, z)>0.
> Finally, the implementor must ensure that compare(x, y)==0 implies that
> sgn(compare(x, z))==sgn(compare(y, z)) for all z.
> Java 7 now is strict and throws exceptions when the contract is violated.
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