stanfordnlp/CoreNLP · error · IllegalArgumentException

Unclosed paren in encoded array: " + encoded

Error message

Unclosed paren in encoded array: " + encoded

What it means

When decoding a parenthesized encoded array string, StringUtils checks that if the string starts with '(' it also ends with ')'. If the closing parenthesis is missing it throws IllegalArgumentException('Unclosed paren in encoded array: <encoded>'). Bracket and brace variants exist with similar messages.

Solutions

  1. Supply the complete string including the closing parenthesis
  2. Validate balance before parsing: check s.startsWith("(") implies s.endsWith(")")
  3. Regenerate the encoded string with the library's encoder instead of reconstructing it manually

Example fix

// before
String enc = "(1,2,3"; // truncated
List<String> terms = StringUtils.decodeArray(enc);
// after
String enc = "(1,2,3)";
List<String> terms = StringUtils.decodeArray(enc);
Defensive patterns

Strategy: validation

Validate before calling

String s = encoded.trim();
if (s.startsWith("(") && !s.endsWith(")")) throw new IllegalArgumentException("Unclosed paren: " + encoded);

Try / catch

try {
  List<String> terms = StringUtils.decodeArray(encoded);
} catch (IllegalArgumentException e) {
  log.error("Bad encoded array: " + e.getMessage());
}

Prevention

When it happens

Trigger: Calling the encoded-array parser (e.g. stringToKey/decode style API in StringUtils) with a string that starts with '(' but does not end with ')', such as '(1,2,3' or a string cut off mid-expression.

Common situations: Truncated files or logs that were cut off; manual string edits dropping the final char; concatenation code that forgot the closing paren; copying encoded values from output that was line-wrapped.

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

AI-assisted analysis of stanfordnlp/CoreNLP@1b7edd19c4 (2026-09-10). Data as JSON: /api/errors/ef2eadc118094098. Report an issue: GitHub.

Appendix: source

Thrown at src/edu/stanford/nlp/util/StringUtils.java:2565

  /**
   * Decode an array encoded as a String. This entails a comma separated value enclosed in brackets
   * or parentheses.
   *
   * @param encoded The String encoding an array
   * @return A String array corresponding to the encoded array
   */
  public static String[] decodeArray(String encoded) {
    if (encoded.isEmpty()) return EMPTY_STRING_ARRAY;
    char[] chars = encoded.trim().toCharArray();

    //--Parse the String
    // (state)
    char quoteCloseChar = (char) 0;
    List<String> terms = new ArrayList<>();
    StringBuilder current = new StringBuilder();
    //(start/stop overhead)
    int start = 0; int end = chars.length;
    if(chars[0] == '('){ start += 1; end -= 1; if(chars[end] != ')') throw new IllegalArgumentException("Unclosed paren in encoded array: " + encoded); }
    if(chars[0] == '['){ start += 1; end -= 1; if(chars[end] != ']') throw new IllegalArgumentException("Unclosed bracket in encoded array: " + encoded); }
    if(chars[0] == '{'){ start += 1; end -= 1; if(chars[end] != '}') throw new IllegalArgumentException("Unclosed bracke in encoded array: " + encoded); }
    // (finite state automaton)
    for (int i=start; i<end; i++) {
      if (chars[i] == '\r') {
        // Ignore funny windows carriage return
        continue;
      } else if (quoteCloseChar != 0) {
        //(case: in quotes)
        if(chars[i] == quoteCloseChar){
          quoteCloseChar = (char) 0;
        }else{
          current.append(chars[i]);
        }
      } else if(chars[i] == '\\'){
        //(case: escaped character)
        if(i == chars.length - 1) throw new IllegalArgumentException("Last character of encoded array is escape character: " + encoded);
        current.append(chars[i+1]);

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