Admobe ads show in android studio

Admove add 

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MobileAds initialize

MobileAds.initialize(this, new OnInitializationCompleteListener() {
    @Override
    public void onInitializationComplete(InitializationStatus initializationStatus) {
    }
});

loadfullscreenads();

AdRequest madRequest = new AdRequest.Builder().build();
mAdView.loadAd(madRequest);
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private void loadfullscreenads(){
    AdRequest adRequest = new AdRequest.Builder().build();
    InterstitialAd.load(this,"ca-app-pub-3940256099942544/1033173712", adRequest,
            new InterstitialAdLoadCallback() {
                @Override
                public void onAdLoaded(@NonNull InterstitialAd interstitialAd) {
                    // The mInterstitialAd reference will be null until
                    // an ad is loaded.
                    mInterstitialAd = interstitialAd;

                    mInterstitialAd.setFullScreenContentCallback(new FullScreenContentCallback(){
                        @Override
                        public void onAdClicked() {
                            // Called when a click is recorded for an ad.
                        }

                        @Override
                        public void onAdDismissedFullScreenContent() {
                            // Called when ad is dismissed.
                            // Set the ad reference to null so you don't show the ad a second time.
                            loadfullscreenads();
                        }

                        @Override
                        public void onAdFailedToShowFullScreenContent(AdError adError) {
                            // Called when ad fails to show.
                            mInterstitialAd = null;
                        }
                        @Override
                        public void onAdImpression() {
                            // Called when an impression is recorded for an ad.
                        }
                        @Override
                        public void onAdShowedFullScreenContent() {
                            // Called when ad is shown.
                        }
                    });
                }
                @Override
                public void onAdFailedToLoad(@NonNull LoadAdError loadAdError) {
                    // Handle the error
                    mInterstitialAd = null;
                }
            });

} 

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=====================================AD SHOW START==============================
if (mInterstitialAd != null) {
    startActivity(new Intent(MainActivity.this,Pag_10.class));
    mInterstitialAd.show(MainActivity.this);
}
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