Confusion in Firebase messaging token documentation

Question

We can get current token by calling this piece of code,

FirebaseMessaging.getInstance().getToken()
    .addOnCompleteListener(new OnCompleteListener<String>() {
        @Override
        public void onComplete(@NonNull Task<String> task) {
          if (!task.isSuccessful()) {
            Log.w(TAG, "Fetching FCM registration token failed", task.getException());
            return;
          }

          // Get new FCM registration token
          String token = task.getResult();

          // Log and toast
          String msg = getString(R.string.msg_token_fmt, token);
          Log.d(TAG, msg);
          Toast.makeText(MainActivity.this, msg, Toast.LENGTH_SHORT).show();
        }
    });

But firebase tells us to register a service which listens for onNewToken() callback It says that new token might be generated under following scenarios

There are two scenarios when onNewToken is called:
 * 1) When a new token is generated on initial app startup
 * 2) Whenever an existing token is changed
 * Under #2, there are three scenarios when the existing token is changed:
 * A) App is restored to a new device
 * B) User uninstalls/reinstalls the app
 * C) User clears app data

I'm confused that if there programmatic access to token, then why there is a service called on token change since there is no condition where token changes mid session?! Can anyone explain with use cases of both of the things above?

Answer 1

You can check out this similar post that explained the difference between the two.