Get reference

[Ratchoss]

Hello, so here, I would like to know how I could get the reference name from the email address firebase as on the image?

My code :

DatabaseReference mDatabaseReference;
mDatabaseReference = FirebaseDatabase.getInstance().getReference();

mDatabaseReference.child(How can it get the Ref name?).orderByChild("mail").equalTo(firebaseUser.getEmail()).addListenerForSingleValueEvent(new ValueEventListener() {
            @Override
            public void onDataChange(DataSnapshot dataSnapshot) {
                for (DataSnapshot child : dataSnapshot.getChildren()) {
                    name.clear();
                    name.add(child.getKey().toString());
                    String s = name.toString().replace("[", "").replace("\"", "").replace("]", "");

           

                }
            }

            @Override
            public void onCancelled(DatabaseError databaseError) {

            }
        });

If you have any question let me know, i'll answer them quickly! Thanks a lot.