When transitioning between fragments, which class's method add is called?

In Android, when transitioning between fragments, the add method is called on a FragmentTransaction object.

The process usually looks like this:

FragmentTransaction transaction = getSupportFragmentManager().beginTransaction();
transaction.add(R.id.container, newFragment);
transaction.commit();

Here:

• getSupportFragmentManager() returns the fragment manager,
• beginTransaction() creates a new transaction,
• add() adds a new fragment to the specified container,
• commit() applies the changes.

Thus, the add method is called on an instance of FragmentTransaction, which manages fragment operations.