Where do I put the private boolean that checks the internet connection?

I am very new to android programming. I'm doing a webview for my website using android studio. I have this code that checks the internet connection:

@Override
        private boolean isNetworkAvailable() {
            ConnectivityManager connectivityManager = (ConnectivityManager) getSystemService(Context.CONNECTIVITY_SERVICE);
            NetworkInfo activeNetworkInfo = connectivityManager.getActiveNetworkInfo();
            return activeNetworkInfo != null && activeNetworkInfo.isConnected();}

And this WebViewClient:

webView.setWebViewClient(new WebViewClient() {
            @Override
            public boolean shouldOverrideUrlLoading(WebView view, String url) {
                if( URLUtil.isNetworkUrl(url) ) {
                    return false;}
                Intent intent = new Intent(Intent.ACTION_VIEW, Uri.parse(url));
                startActivity( intent );
                return true;};

I want to put the code to check the internet inside the WebViewClient, so that the internet is checked when the user browses inside the webview.

Where do I put the check code? And how and what do I put inside the WebViewClient? I tried to put the code to get the internet on an @Override inside the WebViewClient but the error appeared

"Method does not override or implement a method from a superytype".

I don't know how to do, or what does it means.

This is the way I'm using to create the webView:

@Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        PreferenceManager.setDefaultValues(this, R.xml.config, false);
        setRequestedOrientation (ActivityInfo.SCREEN_ORIENTATION_PORTRAIT);
        setContentView(R.layout.activity_main);
        CookieSyncManager.createInstance(this);
        CookieSyncManager.getInstance().startSync();
        this.webView = (WebView) findViewById(R.id.webview);
        WebSettings webSettings = webView.getSettings();
        webSettings.setJavaScriptEnabled(true);
        webView.getSettings().setJavaScriptCanOpenWindowsAutomatically(true);
        webView.loadUrl("...mysite.com");