public static String conv(String number, int fromBase, int toBase) {
        if (!checkRange(fromBase) || !checkRange(toBase)) {
            return null;
        }
        try {
            BigInteger num = new BigInteger(number, Math.abs(fromBase));
            if (fromBase > 0) {
                return num.toString(Math.abs(toBase)).toUpperCase();
            } else {
                return new BigInteger(Long.toUnsignedString(num.longValue()), 10)
                        .toString(Math.abs(toBase)).toUpperCase();
            }
        } catch (NumberFormatException e) {
            return null;
        }
    }
Converts a number from one base to another.

@param number   The number to be converted (as a string or integer).
@param fromBase The base of the input number.
@param toBase   The base to which the number should be converted.
@return The converted number as a string, or null if input is invalid.
inlong-sdk/transform-sdk/src/main/java/org/apache/inlong/sdk/transform/process/function/arithmetic/RadixConvertFunction.java