stanfordnlp/CoreNLP · error · IllegalArgumentException

Unknown mode

Error message

Unknown mode 

What it means

ArrayStringFilter.test() switches over the filter's Mode enum; if mode is not one of the three known values (EXACT, PREFIX, CASE_INSENSITIVE), the default branch throws IllegalArgumentException('Unknown mode ' + mode). This guards against a Mode enum that was extended in a newer library version while the switch was not updated.

Solutions

1. Upgrade/downgrade so the ArrayStringFilter version matches the one that created the filter, ensuring the Mode constant exists in both.
2. Ensure the filter is only constructed with Mode.EXACT, Mode.PREFIX, or Mode.CASE_INSENSITIVE.
3. If you control the enum, add a case for the new constant in the switch before using the filter.

Example fix

// before
Mode mode = MyCustomModes.SUFFIX; // not handled by ArrayStringFilter
ArrayStringFilter f = new ArrayStringFilter(mode, "x");
// after
ArrayStringFilter f = new ArrayStringFilter(ArrayStringFilter.Mode.PREFIX, "x");

if (mode != ArrayStringFilter.Mode.EXACT && mode != ArrayStringFilter.Mode.PREFIX && mode != ArrayStringFilter.Mode.CASE_INSENSITIVE) {
  throw new IllegalArgumentException("unsupported mode: " + mode);
}

boolean isSupportedMode(ArrayStringFilter.Mode m) {
  return m == ArrayStringFilter.Mode.EXACT || m == ArrayStringFilter.Mode.PREFIX || m == ArrayStringFilter.Mode.CASE_INSENSITIVE;
}

try {
  boolean hit = filter.test(input);
} catch (IllegalArgumentException e) {
  // recreate the filter with a known Mode and retry
}

When it happens

Trigger: Calling test() on an ArrayStringFilter whose mode is a newly added or unknown Mode constant not handled by this switch, e.g. a filter constructed in a different library version or via reflection/deserialization with an unexpected mode.

Common situations: Mixing library versions (serializing/deserializing filters across versions where Mode has extra constants); extending the Mode enum locally without updating test(); Java enum deserialization producing a constant unknown to the installed version.

Related errors

• Arabic does not support feature type: " + feat.toString()
• Don't know anything about tagset
• entitySubclassify: unknown style:
• ERROR: unknown dependency type
• is not a legal LogPrior.

AI-assisted analysis of stanfordnlp/CoreNLP@1b7edd19c4 (2026-09-10). Data as JSON: /api/errors/bf1b31b2a00a927a. Report an issue: GitHub.

Appendix: source

Thrown at src/edu/stanford/nlp/util/ArrayStringFilter.java:66

    case PREFIX:
      if (input == null) {
        return false;
      }
      for (int i = 0; i < length; ++i) {
        if (input.startsWith(words[i])) {
          return true;
        }
      }
      return false;
    case CASE_INSENSITIVE:
      for (int i = 0; i < length; ++i) {
        if (words[i].equalsIgnoreCase(input)) {
          return true;
        }
      }
      return false;
    default:
      throw new IllegalArgumentException("Unknown mode " + mode);
    }
  }

  @Override
  public String toString() {
    return mode.toString() + ':' + StringUtils.join(words, ",");
  }

  @Override
  public int hashCode() {
    int result = 1;
    for (String word : words) {
      result += word.hashCode();
    }
    return result;
  }

  @Override

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