[
https://issues.apache.org/jira/browse/UIMA-5845?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16556225#comment-16556225
]
Marshall Schor commented on UIMA-5845:
--------------------------------------
The difference between get and single, is that get doesn't care if there are
more than 1 item in the selection, whereas, single always throws an exception
if there is an item "beyond" the item being gotten.
This exception is different from the situation where there's 0 items in the
selection. For that, the nullOK applies. So for single, a 0 selection "may"
throw and exception, and a > 1 in the selection beyond the item always throws
an exception.
The main idea I think is that people will choose single over get only when they
want an exception thrown when there's > 1 item in the selection beyond the item
being retrieved.
> Inconsistent behavior on going beyond index limits in SelectFS
> --------------------------------------------------------------
>
> Key: UIMA-5845
> URL: https://issues.apache.org/jira/browse/UIMA-5845
> Project: UIMA
> Issue Type: Bug
> Components: Core Java Framework
> Affects Versions: 3.0.0SDK
> Reporter: Richard Eckart de Castilho
> Priority: Major
>
> The behavior of trying to address annotations outside the index appears to be
> inconsistent.
> For example, the following call returns `null`:
> {code}
> String text = "one two three";
> tokenBuilder.buildTokens(jCas, text);
> List<Token> tokens = new ArrayList<Token>(select(jCas, Token.class));
>
> for (Token token : tokens) {
> new AnalyzedText(jCas, token.getBegin(), token.getEnd()).addToIndexes();
> }
>
> Token firstToken = tokens.get(0);
> AnalyzedText x = jCas.select(AnalyzedText.class).preceding(firstToken,
> 0).get();
> {code}
> However, this code trying go from the end of the index to before the first
> item throws a CASRuntime exception:
> {code}
> String text = "Rot wood cheeses dew?";
> tokenBuilder.buildTokens(jCas, text);
> assertThatExceptionOfType(CASRuntimeException.class)
> .isThrownBy(() -> jCas.select(Token.class).backwards().get(4))
> .withMessage("CAS does not contain any '" + Token.class.getName() +
> "' instances shifted by: 4.");
> {code}
> It would seem reasonably to either always return null or to always thrown an
> exception. If an exception is thrown, it would seem reasonable to introduce a
> subtype of the CASRuntimeException, e.g. a CASIndexOutOfBounds exception or
> something the likes. CASRuntimeException seems very general.
--
This message was sent by Atlassian JIRA
(v7.6.3#76005)
