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   
        }
    }
}

Hope this helps ;P

@PasanBhanu
please explain why you are using

        NetworkRequest.Builder builder = new NetworkRequest.Builder();

@PasanBhanu please explain why you are using

        NetworkRequest.Builder builder = new NetworkRequest.Builder();

Reminiscent of older code, Before we found about registerDefault from google team, older version of code was basically build a network request object, add the wifi module and/or bluetooth module (basically any and all network interface you want to observe) and then use that object to registerNetworkCallback

When you use registerDefaultNetworkCallback, it basically connects to the lower level network pool with default options, so you don't need to (but you still can if you want) build your own network object.