@Override public String getMessage(String sector, String agent, String key, int lag) { final String result; final int t = timer.getPeriod().intValue() - lag; final SectorDataset sectorDataset = getSectorDataset(sector, t); if (sectorDataset != null) { result = sectorDataset.getAgentInfo(agent, key); } else { result = null; // TODO générer une erreur ? } return result; }