When we implements an interface in a class, its abstract methods are implemented in the class.Lets see the example. First we created an interface ApplicationInterface ApplicationInterface .java public interface ApplicationInterface { public void activityStarted(); public void activityAborted(); public void activityStopped(); public void activityDone(); } public class MainActivity extends Activity implements ApplicationInterface { @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.activity_main); } // these are the methods implemented using interface @Override public void activityStarted() { // TODO Auto-generated method stub } @Override public void activityAborted() { // TODO Auto-generated method stub } @Override public void activityStopped() { // TODO Auto-generated method stub } @Override public void activityDone() { // TODO Auto-generated...