class RGroupList {

    public void setOccurrence(String occurrence) throws CDKException {
        if (occurrence == null || occurrence.equals("")) {
            occurrence = ">0"; //revert to default
        } else {
            occurrence = occurrence.trim().replaceAll(" ", "");
            if (isValidOccurrenceSyntax(occurrence)) {
                this.occurrence = occurrence;
            } else
                throw new CDKException("Invalid occurence line: " + occurrence);
        }
    }

    public  RGroupList(int rGroupNumber);
    public  RGroupList(int rGroupNumber, boolean restH, String occurrence, int requiredRGroupNumber);

}