TheAlgorithms/Java · error · WordsToNumberException

UNKNOWN_WORD

UNKNOWN_WORD

Error message

Invalid Input. Unknown Word: {word}

What it means

Thrown at the end of the main parsing loop when a word does not match any known category: not 'and', not 'hundred', not a power of ten, not a NumberWord, not 'point', not 'negative'. The default branch of the second switch falls through to this throw. The offending word is interpolated into the message.

Source

Thrown at src/main/java/com/thealgorithms/conversions/WordsToNumber.java:261

                currentChunk = handleNumber(chunks, currentChunk, word, number);
                continue;
            }

            switch (word) {
                case "point" -> {
                    handlePoint(chunks, currentChunk, wordDeque);
                    currentChunk = BigDecimal.ZERO;
                    continue;
                }
                case "negative" -> {
                    handleNegative(isNegative);
                }
                default -> {

                }
            }

            throw new WordsToNumberException(WordsToNumberException.ErrorType.UNKNOWN_WORD, word);
        }

        if (currentChunk.compareTo(BigDecimal.ZERO) != 0) {
            chunks.add(currentChunk);
        }

        BigDecimal completeNumber = combineChunks(chunks);
        return isNegative ? completeNumber.multiply(BigDecimal.valueOf(-1))
                :
                    completeNumber;
                }

                private static boolean isAdditionSafe(BigDecimal currentChunk, BigDecimal number) {
                    int chunkDigitCount = currentChunk.toString().length();
                    int numberDigitCount = number.toString().length();
                    return chunkDigitCount > numberDigitCount;
                }

View on GitHub (pinned to fdfb9a395b)

Solutions

  1. Ensure all words are valid English number words from the supported vocabulary (zero-nineteen, twenty-ninety by tens, hundred, thousand, million, billion, trillion, point, negative, and).
  2. Spell-check and delimiter-check the input.
  3. If supporting other scales, pre-map them to the canonical vocabulary.

Example fix

// before
WordsToNumber.convert('one hunderd');
// after
WordsToNumber.convert('one hundred'); // 100
Defensive patterns

Strategy: validation

Validate before calling

static final Set<String> VOCAB = Set.of(
    "zero","one","two","three","four","five","six","seven","eight","nine","ten","eleven","twelve","thirteen","fourteen","fifteen","sixteen","seventeen","eighteen","nineteen","twenty","thirty","forty","fifty","sixty","seventy","eighty","ninety","hundred","thousand","million","billion","trillion","point","negative","and");
static boolean allWordsKnown(String s) {
    for (String w : s.trim().toLowerCase(Locale.ROOT).split("[ ,-]+")) {
        if (!VOCAB.contains(w)) return false;
    }
    return true;
}

Try / catch

try { WordsToNumber.convert(input); } catch (WordsToNumberException e) {
    if (e.errorType == ErrorType.UNKNOWN_WORD) throw new ApiException(400, "Unrecognized word in input: " + e.getMessage());
    throw e;
}

Prevention

When it happens

Trigger: convert('five baz'), convert('hello world'), convert('one hunderd') (typo), convert('twenty twohundred') (no space), convert('3.14') (numeric digits not words).

Common situations: Typos; non-English words; numeric digits instead of spelled-out words; concatenated words without delimiters; unsupported scale words like 'crore' or 'lakh'.

Related errors

AI-assisted analysis of TheAlgorithms/Java@fdfb9a395b (2026-08-13). Data as JSON: /api/errors/5a35c19d861ae614. Report an issue: GitHub.