stanfordnlp/CoreNLP · error · IndexOutOfBoundsException

Invalid region end=

Error message

Invalid region end=

What it means

region(start, end) validates that end lies within [0, elements.size()]; when end is negative or beyond the list size it throws IndexOutOfBoundsException with 'Invalid region end='. This keeps the exclusive end bound inside the sequence.

Solutions

1. Clamp end to [0, elements.size()] before calling region()
2. Verify the end index is the exclusive bound and does not exceed elements.size()
3. Catch IndexOutOfBoundsException if the window is user-provided
4. Recompute end from the live elements list size

Example fix

// before
matcher.region(start, start + windowLen); // may exceed size
// after
matcher.region(start, Math.min(start + windowLen, elements.size()));

if (end < 0 || end > elements.size()) {
  throw new IllegalArgumentException("region end out of range: " + end);
}
matcher.region(start, end);

boolean isValidEnd(int end, List<?> elements) {
  return end >= 0 && end <= elements.size();
}

try {
  matcher.region(start, end);
} catch (IndexOutOfBoundsException e) {
  log.warn("Invalid region end", e);
  matcher.region(start, elements.size());
}

When it happens

Trigger: Calling matcher.region(start, end) with end < 0 or end > elements.size(), e.g. passing an exclusive end equal to size+1 or a negative window.

Common situations: Using length instead of size for the exclusive bound, stale offsets after the elements list changed, or computing end = start + windowLength that overruns the sequence.

Related errors

• Invalid region start=
• Annotation field cannot be null
• Attribute already defined:
• Attribute already defined
• Attribute match already defined:

AI-assisted analysis of stanfordnlp/CoreNLP@1b7edd19c4 (2026-09-10). Data as JSON: /api/errors/2fd46eb697840cb9. Report an issue: GitHub.

Appendix: source

Thrown at src/edu/stanford/nlp/ling/tokensregex/SequenceMatcher.java:602

      return "Matching not completed";
    } else if (!matched) {
      return "No match found";
    } else {
      return "Match successful";
    }
  }

  /**
   * Set region to search in.
   * @param start - start index
   * @param end - end index (exclusive)
   */
  public void region(int start, int end) {
    if (start < 0 || start > elements.size()) {
      throw new IndexOutOfBoundsException("Invalid region start=" + start + ", need to be between 0 and " + elements.size());
    }
    if (end < 0 || end > elements.size()) {
      throw new IndexOutOfBoundsException("Invalid region end=" + end + ", need to be between 0 and " + elements.size());
    }
    if (start > end) {
      throw new IndexOutOfBoundsException("Invalid region end=" + end + ", need to be larger then start=" + start);
    }
    this.regionStart = start;
    this.nextMatchStart = start;
    this.regionEnd = end;
  }

  public int regionEnd()
  {
    return regionEnd;
  }

  public int regionStart()
  {
    return regionStart;
  }

View on GitHub (pinned to 1b7edd19c4)