TheAlgorithms/Java · error · NumberFormatException

invalid character:{}

Error message

invalid character:{}

What it means

Thrown by the private AnyBaseToDecimal.valOfChar() helper when a character is neither a digit (0-9) nor an uppercase letter (A-Z). Lowercase letters, symbols, and whitespace are all rejected. This limits convertToDecimal to inputs using digits and uppercase A-Z only.

Source

Thrown at src/main/java/com/thealgorithms/conversions/AnyBaseToDecimal.java:49

            power *= radix;
        }
        return result;
    }

    /**
     * Convert a character to its integer value.
     *
     * @param character the character to be converted
     * @return the integer value represented by the character
     * @throws NumberFormatException if the character is not an uppercase letter or a digit
     */
    private static int valOfChar(char character) {
        if (Character.isDigit(character)) {
            return character - CHAR_OFFSET_FOR_DIGIT;
        } else if (Character.isUpperCase(character)) {
            return character - CHAR_OFFSET_FOR_UPPERCASE;
        } else {
            throw new NumberFormatException("invalid character:" + character);
        }
    }
}

View on GitHub (pinned to fdfb9a395b)

Solutions

1. Normalize input to uppercase before calling convertToDecimal(): input.toUpperCase(Locale.ROOT).
2. Strip any non-alphanumeric characters (spaces, signs, '0x' prefixes) before conversion.
3. If lowercase or extended alphabets are required, use Integer.parseInt(input, radix) which accepts lowercase.

Example fix

// before
int dec = AnyBaseToDecimal.convertToDecimal("ff", 16); // lowercase 'f' rejected

// after
int dec = AnyBaseToDecimal.convertToDecimal("ff".toUpperCase(Locale.ROOT), 16);

String normalized = input.toUpperCase(Locale.ROOT).replaceAll("[^0-9A-Z]", "");
for (char c : normalized.toCharArray()) {
    if (!Character.isDigit(c) && !Character.isUpperCase(c)) {
        throw new IllegalArgumentException("invalid char: " + c);
    }
}
int dec = AnyBaseToDecimal.convertToDecimal(normalized, radix);

static boolean isUppercaseAlphaNumeric(String s) {
    for (char c : s.toCharArray()) {
        if (!Character.isDigit(c) && !Character.isUpperCase(c)) return false;
    }
    return true;
}

try {
    int dec = AnyBaseToDecimal.convertToDecimal(input, radix);
} catch (NumberFormatException e) {
    // normalize and retry, or surface to user
    throw new DomainException("Unparseable number: " + input, e);
}

When it happens

Trigger: Passing lowercase hex digits ("ff"). Passing input with whitespace, punctuation, or a sign character ('+', '-'). Passing non-ASCII or Unicode digits.

Common situations: Hex input from a source that emits lowercase. User input containing leading/trailing spaces. Numbers prefixed with '0x' or '0X'. Locale differences producing non-ASCII digits.

Understand the failure class

• Parsing and encoding errors: unexpected token, malformed input — why parsers reject input and how to find the real culprit.

Related errors

• For input string: {}
• Bases must be between 2 and 10.
• Invalid Base64 character: {}
• Slope and intercept must be valid numbers.
• Input cannot be null

AI-assisted analysis of TheAlgorithms/Java@fdfb9a395b (2026-08-13). Data as JSON: /api/errors/784671f9e1070237. Report an issue: GitHub.