dailyDiary = FirebaseDatabase.getInstance().getReference("Daily_Diary");
dailyDiary.addValueEventListener(new ValueEventListener() {
             @Override
                 public void onDataChange(DataSnapshot dataSnapshot) {
                 PersonalInformation pi;
                 // pi =  (PersonalInformation)dataSnapshot.getValue(PersonalInformation.class);
                 for (DataSnapshot DairySnapshot : dataSnapshot.child(user.getUid()).getChildren()) {
                     dd.add(DairySnapshot.getValue(DailyDiary.class));
                 }
             }
                 @Override
                 public void onCancelled(DatabaseError databaseError) {
                     // ...
                 }
             });