stanfordnlp/CoreNLP · error · RuntimeException

Line format error at line

Error message

Line format error at line ${lineNo}: ${line}

What it means

ColumnDataClassifier.readDataset splits each input line into tab-separated fields; a line yielding fewer than 2 fields cannot contain even a class label plus one feature column, so it throws a RuntimeException reporting the line number and content. This is a data-file format validation error, not a code bug.

Solutions

1. Open the reported line and ensure it has at least one tab separating the gold label from feature columns
2. Check the file for space-separated values and re-export with real tab delimiters
3. Remove or fix blank/stray lines near the reported lineNo

Example fix

// before (data.tsv)
label value1 value2
// after (real tab characters)
label	value1	value2

try (var lines = Files.readAllLines(Paths.get(file))) { int i=0; for (String l : lines) { i++; if (!l.trim().isEmpty() && !l.matches("\\s#.*") && l.split("\t").length < 2) throw new IllegalStateException("Line " + i + " has <2 tab-separated fields"); } }

null

try { readDataset(path); } catch (RuntimeException e) { log.error("Data file format problem: " + e.getMessage()); }

When it happens

Trigger: A training/test data line containing no tab separator (single column or blank-but-not-skipped line), encountered during readDataset (called by dataInfo or readTestExamples).

Common situations: Data files saved with spaces instead of tabs; copy-pasted rows losing tabs; trailing malformed lines; editors converting tabs to spaces on save.

Understand the failure class

Background: "Invalid ... format", "must be in format X", "does not look like a ..." — invalid argument format errors across CLI tools and libraries — this error's family across 17 libraries.

Related errors

• Error: Line has too few tab-separated columns
• Dataset could not be loaded
• Not enough columns for format
• Unrecognized format specification in
• addFeature was called with a features object that is…

AI-assisted analysis of stanfordnlp/CoreNLP@1b7edd19c4 (2026-09-10). Data as JSON: /api/errors/591ba111352e5af6. Report an issue: GitHub.

Appendix: source

Thrown at src/edu/stanford/nlp/classify/ColumnDataClassifier.java:455

        int minColumns = Integer.MAX_VALUE;
        int maxColumns = 0;
        for (String line : ObjectBank.getLineIterator(new File(filename), globalFlags.encoding)) {
          lineNo++;
          if (globalFlags.inputFormat == InputFormat.HEADER) {
            if (lineNo == 1) {
              if (storedHeader == null) {
                storedHeader = line; // store it because need elements of it to print header in output
              }
              continue;
            }
          } else if (globalFlags.inputFormat == InputFormat.COMMENTS) {
            if (line.matches("\\s#.*")) {
              continue;
            }
          }
          String[] strings = splitLineToFields(line);
          if (strings.length < 2) {
            throw new RuntimeException("Line format error at line " + lineNo + ": " + line);
          }
          if (strings.length < minColumns) {
            minColumns = strings.length;
          }
          if (strings.length > maxColumns) {
            maxColumns = strings.length;
          }
          if (inTestPhase) {
            lineInfos.add(strings);
          }
          if (strings.length < flags.length) {
            throw new RuntimeException("Error: Line has too few tab-separated columns (" + maxColumns +
                    ") for " + flags.length + " columns required by specified properties: " + line);
          }
          dataset.add(makeDatumFromStrings(strings));
        }
        if (lineNo > 0 && minColumns != maxColumns) {
          logger.info("WARNING: Number of tab-separated columns in " +

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