Using data from Firestore outside of onSuccess

Question

I have some data in my Firestore database and I had like to use it.

MyData.get().addOnSuccessListener( new OnSuccessListener<DocumentSnapshot>() {
    @Override
    public void onSuccess(DocumentSnapshot documentSnapshot) {
        if (documentSnapshot.exists()){
            Map<String, Object> MyData = documentSnapshot.getData();
        }else {
            Toast.makeText( MyActivity.this,"no document",Toast.LENGTH_SHORT ).show();
        }
    }
} ).addOnFailureListener( new OnFailureListener() {
    @Override
    public void onFailure(@NonNull Exception e) {
        Toast.makeText( MyActivity.this,"error",Toast.LENGTH_SHORT ).show();
    }
} );

Now, I had like to use MyData from outside of this listener.

I had like to send this data into some classes I have made to populate a list.

How can I do it?

Thank you