Check for internet connection enabled or not in android

public class MainActivity extends AppCompatActivity {
    private WebView webView;
    @TargetApi(Build.VERSION_CODES.JELLY_BEAN)
    @Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);
    getSupportActionBar().hide();
    webView = (WebView) findViewById(R.id.webView);
    webView.getSettings().setJavaScriptEnabled(true);
    webView.getSettings().setAllowFileAccessFromFileURLs(true);
    webView.getSettings().setAllowUniversalAccessFromFileURLs(true);
    webView.setWebViewClient(new WebViewClient());
    webView.getSettings().setPluginState(WebSettings.PluginState.ON);
    webView.loadUrl("file:///android_asset/index.html");
    if(isNetworkConnected()){

    }else{
        new AlertDialog.Builder(this)
        .setIcon(android.R.drawable.ic_dialog_alert)
        .setTitle("Closing Activity")
        .setMessage("No Internet connection?")
        .setPositiveButton("Exit", new DialogInterface.OnClickListener()
        {
            @Override            public void onClick(DialogInterface dialog, int which) {
                finish();
            }
        })
        .show();
    }
}

@Overridepublic void onBackPressed() {
    new AlertDialog.Builder(this)
            .setIcon(android.R.drawable.ic_dialog_alert)
            .setTitle("Closing Activity")
            .setMessage("Are you sure you want to close this Application?")
            .setPositiveButton("Yes", new DialogInterface.OnClickListener()
            {
                @Override                public void onClick(DialogInterface dialog, int which) {
                    finish();
                }

            })
            .setNegativeButton("No", null)
            .show();
}

}