@Override
    public Object parse(SourceData sourceData, int rowIndex, Context context) {
        Object stringObject = stringParser.parse(sourceData, rowIndex, context);
        if (stringObject == null) {
            return false;
        }
        String string = OperatorTools.parseString(stringObject).toLowerCase();
        if (string.isEmpty()) {
            return false;
        }
        for (char chr : string.toCharArray()) {
            if (chr < '0' || chr > '9') {
                return false;
            }
        }
        return true;
    }
IsDigitFunction  ->  is_digit(string)
description:
- return true if all characters in string are digit.
- return false otherwise (Including cases where string is null and '').
inlong-sdk/transform-sdk/src/main/java/org/apache/inlong/sdk/transform/process/function/string/IsDigitFunction.java