json - Firebase returning null for Data values in Android -

all data.getvalue() returning null. can child key return fine. can write firbase fine. data.getvalue returning null unknown reason. have other classes working fine using exact same format.

//method retrieving info firebase has notifications private void retrieveinfo(){     firebase ref = new firebase("https://fitnectapp.firebaseio.com/");      // attach listener read data @ our posts reference     ref.addchildeventlistener(new childeventlistener() {         // retrieve new posts added database         @override         public void onchildadded(datasnapshot snapshot, string previouschildkey) {             getupdates(snapshot);         }         @override         public void onchildremoved(datasnapshot snapshot) {             getupdates(snapshot);         }         @override         public void onchildchanged(datasnapshot snapshot, string previouschildkey) {             getupdates(snapshot);         }         @override         public void onchildmoved(datasnapshot snapshot, string previouschildkey) {         }         @override         public void oncancelled(firebaseerror firebaseerror) {         }     }); }  //all data values returning null?? private void getupdates(datasnapshot ds) {     if (ds.getkey().equals("notifications")) {         (datasnapshot data : ds.getchildren()) {             string user = sp.getstring("username", null);             notification notification = data.getvalue(notification.class);             if(notification.getnotifuser().equals(user)){                 string sender = notification.getnotifsender();                 string workout = notification.getnotifworkout();                 string notificationtxt = sender + " has liked workout, " + workout;                 notifications.add(notificationtxt);             }          }     } }