stanfordnlp/CoreNLP · error · RuntimeException

Classifier is not initialized

Error message

Classifier is not initialized

What it means

A guard error signaling that cross-validation or testing code in ColumnDataClassifier was invoked before a classifier was trained or loaded; the `classifier` field is null because neither trainClassifier nor loadClassifier ran first.

Solutions

1. Call trainClassifier or loadClassifier before testing/evaluation
2. Check the pipeline order so training precedes cross-validation
3. For command-line use, supply both trainFile and testFile or a serializedClassifier

When it happens

Trigger: Thrown at src/edu/stanford/nlp/classify/ColumnDataClassifier.java:2216 when the library encounters an invalid state.

Common situations: See trigger scenarios.

AI-assisted analysis of stanfordnlp/CoreNLP@1b7edd19c4 (2026-09-10). Data as JSON: /api/errors/cd72bcc8894332b9. Report an issue: GitHub.

Appendix: source

Thrown at src/edu/stanford/nlp/classify/ColumnDataClassifier.java:2216

      }

      List<String[]> devTestLineInfos = lineInfos.subList(start, end);
      Pair<Double,Double> accuracies = testExamples(cl, devTest, devTestLineInfos);
      accuracySum += accuracies.first();
      macroF1Sum += accuracies.second();
    }
    double averageAccuracy = accuracySum / numFolds;
    double averageMacroF1 = macroF1Sum / numFolds;
    NumberFormat nf2 = new DecimalFormat("0.00000");
    logger.info("Average accuracy/micro-averaged F1: " + nf2.format(averageAccuracy));
    logger.info("Average macro-averaged F1: " + nf2.format(averageMacroF1));
    logger.info("");
    return new Pair<>(averageAccuracy, averageMacroF1);
  }

  public String classOf(Datum<String,String> example) {
    if (classifier == null) {
      throw new RuntimeException("Classifier is not initialized");
    }
    return classifier.classOf(example);
  }

  public Counter<String> scoresOf(Datum<String,String> example) {
    if (classifier == null) {
      throw new RuntimeException("Classifier is not initialized");
    }
    return classifier.scoresOf(example);
  }

  public Classifier<String,String> getClassifier() {
    if (classifier == null) {
      throw new RuntimeException("Classifier is not initialized");
    }
    return classifier;
  }

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