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.

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

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

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

• NULL_INPUT
• Base must be greater than 01
• Base must be greater than 02
• Cannot delete from an empty tree
• Cannot enqueue null data

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

Appendix: 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;
                }

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