stanfordnlp/CoreNLP · error · RuntimeException

Error: -train option must have treebankPath as first…

Error message

Error: -train option must have treebankPath as first argument.

What it means

The -train option of ChineseLexiconAndWordSegmenter.main requires at least two sub-arguments, with the treebank path as the first one. If only one (or zero) sub-arguments follow -train, the option parser throws RuntimeException because it cannot determine where the training treebank lives.

Solutions

Provide the treebank path as the first argument after -train plus at least one more argument, e.g. -train /path/to/treebank 100-9999
Verify the command line includes the expected number of sub-arguments (the parser reads numSubArgs(args, argIndex) from the value preceding them)
Consult the usage documentation for -train's expected argument format

Example fix

// before
java ... -train /path/to/chineseTreebank
// after
java ... -train /path/to/chineseTreebank 100-9999

Defensive patterns

Strategy: validation

Validate before calling

if (args contains "-train") { String[] sub = nextArgs(args, idx); if (sub.length < 2) throw new IllegalArgumentException("-train needs treebankPath plus filter args"); }

Try / catch

try { ChineseLexiconAndWordSegmenter.main(args); } catch (RuntimeException e) { if (e.getMessage().contains("-train option")) printUsage(); }

Prevention

Always pass treebankPath as the first -train sub-argument
Build command lines programmatically and validate arg counts before invoking main

When it happens

Trigger: Running the segmenter's main() with a -train flag that lists fewer than 2 arguments, e.g. -train only a file path with no second argument, when the code requires numSubArgs > 1 to read treebankPath.

Common situations: Command-line invocations of the Chinese parser trainer missing the second argument (e.g. tree range/filter parameters), copy-pasted command lines where a filter argument was dropped, or scripting errors.

Understand the failure class

Background: "missing required argument" and "the following required arguments were not provided": what required-argument errors mean and how to fix them — this error's family across 20 libraries.

Related errors

AI-assisted analysis of stanfordnlp/CoreNLP@1b7edd19c4 (2026-09-10). Data as JSON: /api/errors/16a8107d2d8c3aec. Report an issue: GitHub.

Appendix: source

Thrown at src/edu/stanford/nlp/parser/lexparser/ChineseLexiconAndWordSegmenter.java:438

                         "LexicalizedParser parserFileOrUrl filename*");
      return;
    }

    Options op = new Options();
    op.tlpParams = new ChineseTreebankParserParams();

    // while loop through option arguments
    while (argIndex < args.length && args[argIndex].charAt(0) == '-') {
      if (args[argIndex].equalsIgnoreCase("-train")) {
        train = true;
        saveToSerializedFile = true;
        int numSubArgs = numSubArgs(args, argIndex);
        argIndex++;
        if (numSubArgs > 1) {
          treebankPath = args[argIndex];
          argIndex++;
        } else {
          throw new RuntimeException("Error: -train option must have treebankPath as first argument.");
        }
        if (numSubArgs == 2) {
          trainFilter = new NumberRangesFileFilter(args[argIndex++], true);
        } else if (numSubArgs >= 3) {
          try {
            int low = Integer.parseInt(args[argIndex]);
            int high = Integer.parseInt(args[argIndex + 1]);
            trainFilter = new NumberRangeFileFilter(low, high, true);
            argIndex += 2;
          } catch (NumberFormatException e) {
            // maybe it's a ranges expression?
            trainFilter = new NumberRangesFileFilter(args[argIndex], true);
            argIndex++;
          }
        }
      } else if (args[argIndex].equalsIgnoreCase("-encoding")) { // sets encoding for TreebankLangParserParams
        encoding = args[argIndex + 1];
        op.tlpParams.setInputEncoding(encoding);

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