stanfordnlp/CoreNLP · error · IllegalArgumentException

Cannot parse Trilean from string: " + value

Error message

Cannot parse Trilean from string: " + value

What it means

Trilean.fromString(value) throws IllegalArgumentException when the input string matches none of the accepted spellings (true/t/yes/y/1, false/f/no/n/0, unknown/unk/u, case-insensitively). It is a strict parser for user-provided Trilean literals.

Solutions

1. Pass only the documented spellings: true/t/yes/y/1, false/f/no/n/0, unknown/unk/u (case-insensitive).
2. Trim and normalize the input before calling fromString.
3. Pre-validate with a regex/canonicalization step and give the user a clear message on mismatch.
4. Catch IllegalArgumentException and fall back to UNKNOWN with a warning.

Example fix

// before
Trilean t = Trilean.fromString(props.getProperty("flag")); // "enabled"
// after
String v = props.getProperty("flag", "unknown").trim().toLowerCase();
if (!v.matches("true|t|yes|y|1|false|f|no|n|0|unknown|unk|u"))
  throw new IllegalArgumentException("Unsupported flag value: " + v);
Trilean t = Trilean.fromString(v);

String v = value == null ? "" : value.trim().toLowerCase();
if (!v.matches("true|t|yes|y|1|false|f|no|n|0|unknown|unk|u"))
  throw new IllegalArgumentException("Not a Trilean literal: " + value);

try {
  Trilean t = Trilean.fromString(value);
} catch (IllegalArgumentException e) {
  Trilean t = Trilean.UNKNOWN; // or rethrow with friendlier message
}

When it happens

Trigger: fromString("True ") with trailing whitespace variants not trimmed? (matching is exact after lowercase), or any unrecognized token such as "TRUE!" or "maybe" passed to fromString.

Common situations: Parsing config files or command-line flags where users typed values outside the accepted set (e.g. "on", "enabled", "YESS"); untrimmed input from properties files.

Understand the failure class

Background: Invalid enum value errors: "Unknown type", "Invalid scope", "must be one of" — when a string is not on the library's allowed list — this error's family across 23 libraries.

Related errors

• Too many columns: / (offset: )
• Too few columns: / (offset: )
• Bad data format:
• Bad number put into wordToNumber. Word is: \"" + input +…
• Error in wordToNumber function.

AI-assisted analysis of stanfordnlp/CoreNLP@1b7edd19c4 (2026-09-10). Data as JSON: /api/errors/c4b6ecc5e346c7d1. Report an issue: GitHub.

Appendix: source

Thrown at src/edu/stanford/nlp/util/Trilean.java:225

    } else {
      return FALSE;
    }
  }

  public static Trilean fromString(String value) {
    switch(value.toLowerCase()) {
      case "true":
      case "t":
        return TRUE;
      case "false":
      case "f":
        return FALSE;
      case "unknown":
      case "unk":
      case "u":
        return UNKNOWN;
      default:
        throw new IllegalArgumentException("Cannot parse Trilean from string: " + value);
    }
  }

  /** The static value for True */
  public static Trilean TRUE = new Trilean(true, false);
  /** The static value for False */
  public static Trilean FALSE = new Trilean(false, true);
  /** The static value for Unknown (neither true or false) */
  public static Trilean UNKNOWN = new Trilean(false, false);

}

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