stanfordnlp/CoreNLP · error · RuntimeException

Tree.valueOf() tree construction failed

Error message

Tree.valueOf() tree construction failed

What it means

Tree.valueOf(str, trf) parses a bracketed tree string using the given TreeReaderFactory. If the underlying reader throws IOException during parsing, it is rethrown as a RuntimeException with this message, meaning the tree string could not be read/constructed as a valid Tree.

Solutions

  1. Validate/repair the tree string: balanced parentheses, non-empty, one root node (pennPrint-style format)
  2. Print the offending string; check for truncation upstream in your pipeline
  3. Use the correct TreeReaderFactory for your format, or the default Tree.valueOf(str) for standard PTB bracketed format
  4. Wrap valueOf in try-catch for RuntimeException to handle dirty inputs gracefully

Example fix

// before
Tree t = Tree.valueOf(brokenLine); // IOException wrapped -> RuntimeException
// after
String s = brokenLine.trim();
if (s.isEmpty() || !balanced(s)) { skip(s); }
Tree t = Tree.valueOf(s);
Defensive patterns

Strategy: validation

Validate before calling

String s = str == null ? null : str.trim();
if (s == null || s.isEmpty() || !balancedBrackets(s)) throw new IllegalArgumentException("bad tree string");

Type guard

boolean looksLikeTree(String s) { return s != null && s.trim().startsWith("(") && s.trim().endsWith(")") && balancedBrackets(s.trim()); }

Try / catch

try { Tree t = Tree.valueOf(str); } catch (RuntimeException e) { log.warn("Unparseable tree: {}", str); }

Prevention

When it happens

Trigger: Passing a malformed Penn Treebank string (unbalanced brackets, missing labels, empty input, null) to Tree.valueOf; a TreeReaderFactory whose readTree fails on the format.

Common situations: Trees copied from papers/logs with mangled brackets or line breaks; truncated output from a previous parse step; wrong TreeReaderFactory for the input format.

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/8fd75e4523e0c56a. Report an issue: GitHub.

Appendix: source

Thrown at src/edu/stanford/nlp/trees/Tree.java:2412

      return valueOf(str, new LabeledScoredTreeReaderFactory());
  }

  /**
   * This gives you a tree from a String representation (as a
   * bracketed Tree, of the kind produced by {@code toString()},
   * {@code pennPrint()}, or as in the Penn Treebank.
   * It's not the most efficient thing to do for heavy duty usage.
   *
   * @param str The tree as a bracketed list in a String.
   * @param trf The TreeFactory used to make the new Tree
   * @return The Tree
   * @throws RuntimeException If the Tree format is not valid
   */
  public static Tree valueOf(String str, TreeReaderFactory trf) {
    try {
      return trf.newTreeReader(new StringReader(str)).readTree();
    } catch (IOException ioe) {
      throw new RuntimeException("Tree.valueOf() tree construction failed", ioe);
    }
  }


  /**
   * Return the child at some daughter index.  The children are numbered
   * starting with an index of 0.
   *
   * @param i The daughter index
   * @return The tree at that daughter index
   */
  public Tree getChild(int i) {
    Tree[] kids = children();
    return kids[i];
  }

  /**
   * Destructively removes the child at some daughter index and returns it.

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