String string=new String("[{\"id\":\"2018\",\"ceaNumber\":\"R000001X\",\"fullName\":\"Teszt 1\"},{\"id\":\"2019\",\"ceaNumber\":\"R000002X\",\"fullName\":\"Teszt 2\"}]");
        try {
            JSONArray jsonArr = new JSONArray(string);
            HashMap<String,User> users = new HashMap<String,User>();
            for (int i = 0; i < jsonArr.length(); i++)
            {
                JSONObject jsonObj = jsonArr.getJSONObject(i);
                Iterator iterator = jsonObj.keys();

                String id = null;
                User u=new User();
                while(iterator.hasNext()){
                    String key = (String) iterator.next();
                    if(key.equals("id")){
                        id=(String) jsonObj.get(key);
                        u.id=id;
                    }
                    if(key.equals("ceaNumber")){
                        u.ceaNumber=(String)jsonObj.get(key);
                    }
                    if(key.equals("fullName")){
                        u.fullName=(String)jsonObj.get(key);
                    }
                }
                users.put(id,u);
            }
            System.out.println(users);
        } catch (JSONException e) {
            e.printStackTrace();
        }