Check Internet Connection in Android (API Level 29) Using Network Callback

CheckNetwork.java

/*
You need to call the below method once. It register the callback and fire it when there is a change in network state.
Here I used a Global Static Variable, So I can use it to access the network state in anyware of the application.
*/

// You need to pass the context when creating the class
public CheckNetwork(Context context) {
    this.context = context;
}

// Network Check
public void registerNetworkCallback()
{
    try {
        ConnectivityManager connectivityManager = (ConnectivityManager) context.getSystemService(Context.CONNECTIVITY_SERVICE);
        NetworkRequest.Builder builder = new NetworkRequest.Builder();

        connectivityManager.registerDefaultNetworkCallback(new ConnectivityManager.NetworkCallback(){
                    @Override
                    public void onAvailable(Network network) {
                        Variables.isNetworkConnected = true; // Global Static Variable
                    }
                    @Override
                    public void onLost(Network network) {
                        Variables.isNetworkConnected = false; // Global Static Variable
                    }
                }

        );
        Variables.isNetworkConnected = false;
    }catch (Exception e){
        Variables.isNetworkConnected = false;
    }
}

GlobalVariables.java

public class Variables {
    // Global variable used to store network state
    public static boolean isNetworkConnected = false;
}

MainActivity.java

public class MainActivity extends AppCompatActivity {
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        
        // Register Callback - Call this in your app start!
        CheckNetwork network = new CheckNetwork(getApplicationContext());
        network.registerNetworkCallback();
        
        // Check network connection
        if (Variables.isNetworkConnected){
            // Internet Connected
        }else{
            // Not Connected   
        }
    }
}