public static EnumMap<PizzaStatus, List<Pizza>> 
  groupPizzaByStatus(List<Pizza> pizzaList) {
    EnumMap<PizzaStatus, List<Pizza>> pzByStatus = 
      new EnumMap<PizzaStatus, List<Pizza>>(PizzaStatus.class);

    for (Pizza pz : pizzaList) {
        PizzaStatus status = pz.getStatus();
        if (pzByStatus.containsKey(status)) {
            pzByStatus.get(status).add(pz);
        } else {
            List<Pizza> newPzList = new ArrayList<Pizza>();
            newPzList.add(pz);
            pzByStatus.put(status, newPzList);
        }
    }
    return pzByStatus;
}

        Iterator<Pizza> iterator = pizzaList.iterator();
        while (iterator.hasNext()) {
            Pizza pz = iterator.next();
            PizzaStatus status = pz.getStatus();
            if (pzByStatus.containsKey(status)) {
                pzByStatus.get(status).add(pz);
            } else {
                List<Pizza> newPzList = new ArrayList<>();
                newPzList.add(pz);
                pzByStatus.put(status, newPzList);
            }
        }