stanfordnlp/CoreNLP · error · IllegalArgumentException

2 arguments expected, got

Error message

2 arguments expected, got ${in.size()}

What it means

The typed comparison ValueFunction (e.g. NUMBER compare) requires exactly two arguments and throws IllegalArgumentException when apply() receives any other count. The comparison produces TRUE/FALSE based on comparing the two values.

Solutions

1. Supply exactly two arguments to the comparison function in the expression.
2. Call checkArgs(in) before apply() and handle the false case.
3. Fix dynamic expression builders so missing variables don't reduce the argument count.

Example fix

// before
Value v = ValueFunctions.of("GT").apply(env, Arrays.asList(a));
// after
Value v = ValueFunctions.of("GT").apply(env, Arrays.asList(a, b));

if (args == null || args.size() != 2) throw new IllegalArgumentException("Compare needs exactly 2 args");

boolean isBinary(List<Value> in) { return in != null && in.size() == 2; }

try {
    v = cmpFn.apply(env, args);
} catch (IllegalArgumentException e) {
    if (e.getMessage() != null && e.getMessage().contains("2 arguments expected")) {
        v = null; // handle missing operand
    } else throw e;
}

When it happens

Trigger: Calling a compare-style ValueFunction with in.size() != 2, e.g. apply(env, singletonList(v)) with one value or three values, or expression text like GT(5) missing an operand.

Common situations: Typos in expression strings omitting an operand, programmatic apply() calls without checkArgs, dynamically generated expressions where a variable evaluated to nothing and dropped an argument.

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

• Invalid number of arguments to
• arguments expected, got
• Annotation field cannot be null
• : Entry has multiple types for : . Taking type to be
• Attribute already defined:

AI-assisted analysis of stanfordnlp/CoreNLP@1b7edd19c4 (2026-09-10). Data as JSON: /api/errors/c0c3b6d4f84cd3ac. Report an issue: GitHub.

Appendix: source

Thrown at src/edu/stanford/nlp/ling/tokensregex/types/ValueFunctions.java:787

    public boolean checkArgs(List<Value> in) {
      if (in.size() != 2) {
        return false;
      }
      if (clazz != null) {
        if (in.get(0) == null || in.get(0).get() == null || !(clazz.isAssignableFrom(in.get(0).get().getClass()))) {
          return false;
        }
        if (in.get(1) == null || in.get(1).get() == null || !(clazz.isAssignableFrom(in.get(1).get().getClass()))) {
          return false;
        }
      }
      return true;
    }

    @Override
    public Value apply(Env env, List<Value> in) {
      if (in.size() != 2) {
        throw new IllegalArgumentException("2 arguments expected, got " + in.size());
      }
      if (in.get(0) == null || in.get(1) == null || in.get(0).get() == null || in.get(1).get() == null) {
        return null; // Can't compare...
      }
      Boolean res = compare((T) in.get(0).get(), (T) in.get(1).get());
      return (res)? Expressions.TRUE: Expressions.FALSE;
    }
  }

  public static final ValueFunction NOT_EQUALS_FUNCTION = new NamedValueFunction("EQUALS") {
    @Override
    public String getParamDesc() {
      return "Object,Object";
    }

    @Override
    public boolean checkArgs(List<Value> in) {
      return in.size() == 2;

View on GitHub (pinned to 1b7edd19c4)