Why is Firebase realtime database is repeatedly changing data?

I’m using the below code for inserting data to the Firebase real-time database:

private void addUserDataToFirebase(String name,String phoneNumber,String email){

    firebaseDatabase = FirebaseDatabase.getInstance();
    databaseReference = firebaseDatabase.getReference().child("Users");

    databaseReference.addValueEventListener(new ValueEventListener() {
        @Override
        public void onDataChange(@NonNull DataSnapshot snapshot) {
            HashMap<String , String > usermap = new HashMap<>();

            usermap.put("Name",name);
            usermap.put("Email",email);
            usermap.put("PhoneNumber",phoneNumber);

            databaseReference.child(FirebaseAuth.getInstance().getCurrentUser().getUid()).setValue(usermap);
        }

        @Override
        public void onCancelled(@NonNull DatabaseError error) {
            Toast.makeText(RegisterActivity.this, "data added", Toast.LENGTH_SHORT).show();
        }
    });
}

Answer

If you only want to write the user to the database, there is no need to attach a ValueEventListener. You can only use:

HashMap<String, String > usermap = new HashMap<>();
usermap.put("Name",name);
usermap.put("Email",email);
usermap.put("PhoneNumber",phoneNumber);
String uid = FirebaseAuth.getInstance().getCurrentUser().getUid();
databaseReference.child(uid).setValue(usermap);

There is no need to read anything, or listen for real-time updates, when writing data, unless you need to do some verifications, for example, to check if the user already exists.