Message box and checking internet connection in andorid

In manifest file have to add a new permission
android.permission.ACCESS_NETWORK_STATE



ConnectivityManager cm =
       (ConnectivityManager)getSystemService(Context.CONNECTIVITY_SERVICE);

NetworkInfo activeNetwork = cm.getActiveNetworkInfo();
boolean isConnected = activeNetwork.isConnectedOrConnecting();
if (isConnected != true){
AlertDialog alertDialog;
alertDialog = new AlertDialog.Builder(this).create();
alertDialog.setTitle("Ineternet Connection");
alertDialog.setMessage("Not available");
alertDialog.show();
}
else
{

// rest code
}