public static Event[] all() {
   ArrayList<HashMap<String, Object>> event_arr = modelCollection.all("event"); // get all postures
   ArrayList<Event> collection = new ArrayList<>();
   for (HashMap<String, Object> item : event_arr) {
     Event model = new Event();
     model.id = (int) item.get("id");
     model.createdDate = (Date) item.get("createdDate");
     model.time = (Date) item.get("time");
     String[] list = model.postureList.split(",");
     Converter converter = Converter.getInstance();
     for (int i = 0; i < list.length; i++) {
       model.postures.add(Posture.find(converter.toInt(list[i])));
     }
     model.modifiedDate = (Date) item.get("modifiedDate");
     collection.add(model);
   }
   return collection.toArray(new Event[collection.size()]);
 }
 public static Event find(int id) {
   HashMap<String, Object> event_map = modelCollection.find("event", id);
   if (event_map == null) {
     return null;
   }
   Event event = new Event(); // create event and return its value
   event.id = (int) event_map.get("id");
   event.createdDate = (Date) event_map.get("createdDate");
   event.time = (Date) event_map.get("time");
   event.postureList = (String) event_map.get("postureList");
   String[] list = event.postureList.split(",");
   Converter converter = Converter.getInstance();
   for (int i = 0; i < list.length; i++) {
     event.postures.add(Posture.find(converter.toInt(list[i])));
   }
   event.modifiedDate = (Date) event_map.get("modifiedDate");
   return event;
 }
 public static Event[] where(String colName, String operator, String value) {
   ArrayList<HashMap<String, Object>> event_arr =
       modelCollection.where("event", colName, operator, value);
   ArrayList<Event> collection = new ArrayList<>(); // create array of event and return its value
   for (HashMap<String, Object> item : event_arr) {
     Event model = new Event();
     model.id = (int) item.get("id");
     model.createdDate = (Date) item.get("createdDate");
     model.time = (Date) item.get("time");
     String[] list = model.postureList.split(",");
     Converter converter = Converter.getInstance();
     for (int i = 0; i < list.length; i++) {
       model.postures.add(Posture.find(converter.toInt(list[i])));
     }
     model.modifiedDate = (Date) item.get("modifiedDate");
     collection.add(model);
   }
   return collection.toArray(new Event[collection.size()]);
 }