return allActiveSubUnits;
return new ArrayList<Unit>(allActiveSubUnits);
    public List<Unit> getActiveSubUnits(Date currentDate) {        List<Unit> allActiveSubUnits = new ArrayList<Unit>();        for (Unit subUnit : this.getSubUnits()) {            if (subUnit.isActive(currentDate)) {                allActiveSubUnits.add(subUnit);            }        }        return allActiveSubUnits;    }