How to close the application if there is no Internet?

Question

Android

It is necessary to close the application, in the absence of the Internet, what code to prescribe?
Here is my MainActivity code:

package ua.com.prologistic.hellowebviewapp;

import android.app.Activity;
import android.content.Context;
import android.net.ConnectivityManager;
import android.net.NetworkInfo;
import android.os.Bundle;
import android.support.v7.app.AppCompatActivity;
import android.view.KeyEvent;
import android.view.Window;
import android.webkit.WebChromeClient;
import android.webkit.WebSettings;
import android.webkit.WebView;
import android.webkit.WebViewClient;
import android.widget.Toast;

import java.io.IOException;
import java.net.HttpURLConnection;
import java.net.URL;
import java.security.AccessController;

public class MainActivity extends AppCompatActivity {



    private WebView webView;


    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        webView = (WebView) findViewById(R.id.webView);

        WebSettings webSettings = webView.getSettings();
        webSettings.setJavaScriptEnabled(true);

        SimpleWebViewClientImpl webViewClient = new SimpleWebViewClientImpl(this);
        webView.setWebViewClient(webViewClient);


        webView.loadUrl("https://itcreator.pro/chat/m/");

        
    }


    @Override
    public boolean onKeyDown(int keyCode, KeyEvent event) {
        if ((keyCode == KeyEvent.KEYCODE_BACK) && this.webView.canGoBack()) {
            this.webView.goBack();
            return true;
        }

        return super.onKeyDown(keyCode, event);
    }
}