ExemploAdmob_MainActivity.java

public class MainActivity extends AppCompatActivity {

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        initAds();

    }

    private void initAds(){
        AdView adView = (AdView)findViewById(R.id.adView);
        AdRequest adRequest = new AdRequest.Builder().build();
        adView.loadAd(adRequest);
    }
}