Implementing basic ads in Android

import android.app.Activity;
import android.os.Bundle;
import android.util.Log;

import androidx.appcompat.app.AppCompatActivity;

import com.unity3d.ads.IUnityAdsLoadListener;
import com.unity3d.ads.IUnityAdsShowListener;
import com.unity3d.ads.UnityAdsShowOptions;
import com.unity3d.ads.example.R;

import com.unity3d.ads.IUnityAdsInitializationListener;
import com.unity3d.ads.UnityAds;

public class ShowInterstitialAd extends AppCompatActivity implements IUnityAdsInitializationListener  {

  private String unityGameID = "1234567";
  private Boolean testMode = true;
  private String adUnitId = "video";

  private IUnityAdsLoadListener loadListener = new IUnityAdsLoadListener() {
     @Override
     public void onUnityAdsAdLoaded(String placementId) {
        UnityAds.show((Activity)getApplicationContext(), adUnitId, new UnityAdsShowOptions(), showListener);
     }

     @Override
     public void onUnityAdsFailedToLoad(String placementId, UnityAds.UnityAdsLoadError error, String message) {
        Log.e("UnityAdsExample", "Unity Ads failed to load ad for " + placementId + " with error: [" + error + "] " + message);
     }
  };

  private IUnityAdsShowListener showListener = new IUnityAdsShowListener() {
     @Override
     public void onUnityAdsShowFailure(String placementId, UnityAds.UnityAdsShowError error, String message) {
        Log.e("UnityAdsExample", "Unity Ads failed to show ad for " + placementId + " with error: [" + error + "] " + message);
     }

     @Override
     public void onUnityAdsShowStart(String placementId) {
        Log.v("UnityAdsExample", "onUnityAdsShowStart: " + placementId);
     }

     @Override
     public void onUnityAdsShowClick(String placementId) {
        Log.v("UnityAdsExample", "onUnityAdsShowClick: " + placementId);
     }

     @Override
     public void onUnityAdsShowComplete(String placementId, UnityAds.UnityAdsShowCompletionState state) {
        Log.v("UnityAdsExample", "onUnityAdsShowComplete: " + placementId);
     }
  };

  @Override
  protected void onCreate (Bundle savedInstanceState) {
     super.onCreate (savedInstanceState);
     setContentView (R.layout.activity_main);
     // Initialize the SDK:
     UnityAds.initialize(getApplicationContext(), unityGameID, testMode, this);
  }

  @Override
  public void onInitializationComplete() {
     DisplayInterstitialAd();
  }

  @Override
  public void onInitializationFailed(UnityAds.UnityAdsInitializationError error, String message) {
     Log.e("UnityAdsExample", "Unity Ads initialization failed with error: [" + error + "] " + message);
  }

// Implement a function to load an interstitial ad. The ad will start to show once the ad has been loaded.
  public void DisplayInterstitialAd () {
     UnityAds.load(adUnitId, loadListener);
  }
}