Suppose i have an abstract base class Parent which defines an abstract Method A(some parameter) taking a parameter, also it defines an instance Method B which calls method A(parameter) inside its body and passing some parameter.Then we have an concrete child class B which extends the base class and provide its own implementation of Method A using the parameter passes. I have seen many implementation of this practice in frameworks. I want to know how it works and does it provide any benefits.

Here is some code written in Android

public abstract class ParentActivity extends Activity {
    public abstract void onResume(LoginToken token);

    @Override
        protected void onCreate(Bundle savedInstanceState) {
               super.onCreate(savedInstanceState);
               Some implementation code
        }

    @Override
        public void onResume() {
              super.onResume();
              Some implementation code
              onResume(token);
        }
}

public class ChildActivity extends ParentActivity{
        LoginToken token;
    @Override
        protected void onCreate(Bundle savedInstanceState) {
               super.onCreate(savedInstanceState);
               Some implementation code
        }

    @Override
        public void onResume() {
              Some implementation code
              super.onResume();
        }

    @Override
        public void onResume(LoginToken token) {
             this.token=token;
        }
}