stanfordnlp/CoreNLP · error · IllegalArgumentException

Unclosed bracket in encoded array: " + encoded

Error message

Unclosed bracket in encoded array: " + encoded

What it means

StringUtils' encoded-array decoder (stringToArray-style parsing) expects an array encoded as "(a,b,c)" or "[a,b]". When the string starts with '[' the decoder strips one character from each end and requires the final character to be ']'. If it is not, the encoded array is malformed and this IllegalArgumentException is thrown so the caller fails fast instead of silently mis-parsing.

Solutions

1. Inspect the input string and add the missing ']' as the last character
2. Ensure the program that generates the encoded string appends the matching close bracket
3. Trim stray whitespace/trailing characters before passing the string to the decoder
4. Wrap the call in try-catch on IllegalArgumentException and report the malformed input to the user

Example fix

// before
String[] terms = StringUtils.decode("[foo,bar");
// after
String[] terms = StringUtils.decode("[foo,bar]");

if (s != null && s.startsWith("[") && !s.endsWith("]")) throw new IllegalArgumentException("Encoded array must end with ']': " + s);

static boolean isBracketBalanced(String s) { return s != null && s.length() >= 2 && ((s.charAt(0)=='[' && s.charAt(s.length()-1)==']') || (s.charAt(0)=='(' && s.charAt(s.length()-1)==')') || (s.charAt(0)=='{' && s.charAt(s.length()-1)=='}')); }

When it happens

Trigger: Calling the public StringUtils decode method with a string whose first character is '[' but whose last character is not ']' (e.g. "[a,b", "[a,b)", "[]x").

Common situations: Hand-built or truncated encoded strings pasted into config files; string truncation by logging/copy-paste; off-by-one string slicing when programmatically building the encoded form; stray characters appended after the closing bracket.

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

• Unclosed bracke in encoded array: " + encoded
• Last character of encoded array is escape character: " +…
• Unclosed bracket in encoded map: " + encoded
• Unclosed paren in encoded map: " + encoded
• Cannot find matching labelled span for

AI-assisted analysis of stanfordnlp/CoreNLP@1b7edd19c4 (2026-09-10). Data as JSON: /api/errors/79463cc0acd79dd1. Report an issue: GitHub.

Appendix: source

Thrown at src/edu/stanford/nlp/util/StringUtils.java:2566

   * 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]);
        i += 1;

View on GitHub (pinned to 1b7edd19c4)