stanfordnlp/CoreNLP · error · IllegalArgumentException

Too many columns: / (offset: )

Error message

Too many columns: <columnI>/<numColumns> (offset: <offset>)

What it means

Thrown by IOUtils' CSV/TSV line parser (csvStringToColumns-style readers) when a line contains MORE comma-separated fields than the declared number of columns. While parsing a non-quoted line, encountering a comma that would advance columnI past numColumns-1 raises this IllegalArgumentException with column counts and the character offset in the input.

Solutions

1. Increase the numColumns argument to match the actual maximum number of comma-separated fields per row.
2. Quote fields that contain literal commas in the source data (standard CSV quoting) so the parser treats them as part of one field.
3. Pre-validate the file: count fields per line (outside quotes) and reject/report offending lines before calling the parser.
4. If the delimiter is not a comma, use the correct parsing method/separator instead.

Example fix

// before
List<String[]> cols = IOUtils.csvStringToColumns(csvText, 3);
// after
int maxFields = csvText.lines().mapToInt(l -> l.split(",(?=(?:[^"]*[^"]*")*[^"]*$)").length).max().orElse(0);
List<String[]> cols = IOUtils.csvStringToColumns(csvText, maxFields);

int expectedCols = numColumns;
int lineNo = 0;
for (String line : csvText.split("\n")) {
  lineNo++;
  if (countFields(line) > expectedCols)
    throw new IllegalArgumentException("Line " + lineNo + " has too many fields (unquoted comma?)");
}
static int countFields(String line) {
  int n = 1; boolean inQ = false;
  for (char c : line.toCharArray()) {
    if (c == '"') inQ = !inQ;
    else if (c == ',' && !inQ) n++;
  }
  return n;
}

try {
  List<String[]> cols = IOUtils.csvStringToColumns(csvText, numColumns);
} catch (IllegalArgumentException e) {
  // e.getMessage() contains columnI/numColumns and offset; report line/offset to data owner
  throw new DataFormatException("Bad CSV row: " + e.getMessage());
}

When it happens

Trigger: Calling the CSV reader (e.g. slurpFileAsColumns / csvStringToColumns variants) with a numColumns argument smaller than the actual field count of some row: unquoted commas inside field values, a header declaring fewer columns than data rows, or a wrong numColumns constant in the caller.

Common situations: CSV data exported from Excel with commas inside text that was not quote-escaped; a pipeline expects 3 columns but source data gained a 4th; parsing a TSV file while passing ',' as separator mismatch; hard-coded numColumns not updated after schema change.

Understand the failure class

Background: Schema validation failed / invalid input schema: payload rejected because its shape doesn't match the expected schema — this error's family across 28 libraries.

Related errors

• Too few columns: / (offset: )
• Cannot parse Trilean from string: " + value
• 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/b6e1a1ef8097ffac. Report an issue: GitHub.

Appendix: source

Thrown at src/edu/stanford/nlp/io/IOUtils.java:1451

    //--Read
    for(int offset=0; offset<csvContents.length; offset++){
      if(nextIsEscaped){
        buffer[columnI].append(csvContents[offset]);
        nextIsEscaped = false;
      } else {
        switch(csvContents[offset]){
          case '"':
            //(case: quotes)
            inQuotes = !inQuotes;
            break;
          case ',':
            //(case: field separator)
            if(inQuotes){
              buffer[columnI].append(',');
            } else {
              columnI += 1;
              if(columnI >= numColumns){
                throw new IllegalArgumentException("Too many columns: "+columnI+"/"+numColumns+" (offset: " + offset + ")");
              }
              buffer[columnI] = new StringBuilder();
            }
            break;
          case '\n':
            //(case: newline)
            if(inQuotes){
              buffer[columnI].append('\n');
            } else {
              //((error checks))
              if(columnI != numColumns-1){
                throw new IllegalArgumentException("Too few columns: "+columnI+"/"+numColumns+" (offset: " + offset + ")");
              }
              //((create line))
              String[] rtn = new String[buffer.length];
              for(int i=0; i<buffer.length; i++){ rtn[i] = buffer[i].toString(); }
              lines.add(rtn);
              //((update state))

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