stanfordnlp/CoreNLP · error · IllegalArgumentException

is an unsupported OutputStyle

Error message

 is an unsupported OutputStyle

What it means

PlainTextDocumentReaderAndWriter.printAnswers selects a printing routine based on the configured OutputStyle. The switch's default branch throws IllegalArgumentException if the outputStyle constant is not one of the handled styles — normally only reachable if a new OutputStyle constant was added without updating printAnswers, or the style was set programmatically to an unexpected value.

Solutions

1. Set outputStyle to one of the supported constants handled by printAnswers (e.g. via OutputStyle.fromShortName with a valid short name).
2. If you added a new OutputStyle enum constant, add a case for it in printAnswers.
3. Check for library version mixing (jar on classpath differing from compiled-against version) and align versions.

Example fix

// before
props.setProperty("outputStyle", "fancy");
// after
props.setProperty("outputStyle", "tsv");

OutputStyle style = PlainTextDocumentReaderAndWriter.OutputStyle.fromShortName(props.getProperty("outputStyle"));
// ensure it is one of the styles handled by printAnswers before tagging

try {
  writer.printAnswers(l, out);
} catch (IllegalArgumentException e) {
  if (e.getMessage() != null && e.getMessage().endsWith("is an unsupported OutputStyle")) {
    log.error("Unsupported OutputStyle: " + e.getMessage());
  } else throw e;
}

When it happens

Trigger: Calling printAnswers / getAnswers / runTaggerSGML with a writer whose outputStyle is an OutputStyle constant not covered by the switch (e.g. a newly added enum value or one set via reflection/setOutputStyle).

Common situations: Extending or upgrading Stanford NLP where a custom/new OutputStyle was introduced but printAnswers was not updated; wiring an OutputStyle object directly instead of using fromShortName-parsed values.

Related errors

• is not an OutputStyle
• : Entry doesn't have overwriteable types , but entry type…
• : Ignoring duplicate entry: , old type = , new type =
• : Replacing duplicate entry (higher priority): old= , new=
• Arabic does not support feature type: " + feat.toString()

AI-assisted analysis of stanfordnlp/CoreNLP@1b7edd19c4 (2026-09-10). Data as JSON: /api/errors/c3b800f34aaf5a06. Report an issue: GitHub.

Appendix: source

Thrown at src/edu/stanford/nlp/sequences/PlainTextDocumentReaderAndWriter.java:256

        printAnswersTokenizedInlineXML(l, out);
      }
      break;
      case TSV:
        if (preserveSpacing) {
          printAnswersAsIsTextTsv(l, out);
        } else {
          printAnswersTokenizedTextTsv(l, out);
        }
        break;
      case TABBED:
        if (preserveSpacing) {
          printAnswersAsIsTextTabbed(l, out);
        } else {
          printAnswersTokenizedTextTabbed(l, out);
        }
        break;
    default:
      throw new IllegalArgumentException(outputStyle +
                                         " is an unsupported OutputStyle");
    }
  }

  private static <IN extends CoreMap> void printAnswersTokenizedText(List<IN> l, PrintWriter out) {
    for (IN wi : l) {
      out.print(StringUtils.getNotNullString(wi.get(CoreAnnotations.TextAnnotation.class)));
      out.print('/');
      out.print(StringUtils.getNotNullString(wi.get(CoreAnnotations.AnswerAnnotation.class)));
      out.print(' ');
    }
    out.println(); // put a single newline at the end [added 20091024].
  }

  private static <IN extends CoreMap> void printAnswersAsIsText(List<IN> l, PrintWriter out) {
    for (IN wi : l) {
      out.print(StringUtils.getNotNullString(wi.get(CoreAnnotations.BeforeAnnotation.class)));
      out.print(StringUtils.getNotNullString(wi.get(CoreAnnotations.TextAnnotation.class)));

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