Implementation of Interstitial Ad after Splash Screen

public class ActivitySplash extends AppCompatActivity {

    private InterstitialAd interstitialAd;

    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);

        setContentView(R.layout.activity_splash);

        loadInterstitialAd();

        new CountDownTimer(5000, 1000) {
            @Override
            public void onFinish() {
                Intent intent = new Intent(getBaseContext(), MainActivity.class);
                startActivity(intent);
                finish();

                showInterstitialAd();
            }

            @Override
            public void onTick(long millisUntilFinished) {

            }
        }.start();

    }

    private void loadInterstitialAd() {
        interstitialAd = new InterstitialAd(getApplicationContext());
        interstitialAd.setAdUnitId(getResources().getString(R.string.admob_interstitial_id));
        interstitialAd.loadAd(new AdRequest.Builder().build());
        interstitialAd.setAdListener(new AdListener() {
            @Override
            public void onAdClosed() {

            }
        });
    }

    private void showInterstitialAd() {
        if (interstitialAd.isLoaded()) {
            interstitialAd.show();
        }
    }

}