That's collector

gistfile1.txt

    @SuppressWarnings("unchecked")
    private static <T,U> Map<U, List<T>> formatMapClefEnsembleValeursAvecOuSansLimitateur(List<Map<String, Object>> liste,
            String identifiant, String valeur, Integer limitation) {

        final Map<U, List<T>> mapKeyValue = new HashMap<U, List<T>>();
        final Map<U, Integer> mapLimitation = new HashMap<U, Integer>();
        if (!isEmpty(liste)) {
            final boolean ligneComplete = StrUtil.isEmpty(valeur);
            for (final Map<String, ?> map : liste) {
                final U key = (U) map.get(identifiant);
                if (mapKeyValue.containsKey(key)) {
                    final Integer limitationEnCours = mapLimitation.get(key);
                    if (limitationEnCours < limitation || limitation == 0) {
                        final List<T> listeResult = mapKeyValue.get(key);
                        if (ligneComplete) {
                            listeResult.add((T)map);
                        } else {
                            listeResult.add((T)map.get(valeur));
                        }
                        mapKeyValue.put(key, listeResult);
                        mapLimitation.put(key, limitationEnCours  + 1);
                    }
                } else {
                    final List<T> listeResult = new ArrayList<T>();
                    if (ligneComplete) {
                        listeResult.add((T)map);
                    } else {
                        listeResult.add((T)map.get(valeur));
                    }
                    mapKeyValue.put(key, listeResult);
                    mapLimitation.put(key, 1);
                }
            }
        }
        return mapKeyValue;

    }