class MathsUtil {
    private static final char ASTERISK = '*';

    public static Long calculate(String value) {<FILL_FUNCTION_BODY>}
}

        if (StringUtils.isEmpty(value)) {
            return null;
        }

        long result = 1;
        try {
            String[] array = StringUtils.split(value, ASTERISK);
            for (String data : array) {
                result *= Long.parseLong(data.trim());
            }
        } catch (Exception e) {
            return null;
        }

        return result;
    
<no_super_class>