TO CHECK INTERNET CONNECTION IN ANDROID DEVICE

//Connection Detector is used to to check the connectivity

ConnectionDetector cd;
      
cd = new ConnectionDetector(getApplicationContext());
           
Boolean isInternetPresent = cd.isConnectingToInternet();
            
           // check for Internet status
           if (isInternetPresent) {
               // Internet Connection is Present
               // make HTTP requests
               //put your code if internet is present
           } else {
               // Internet connection is not present
          

/*putting a dialog box for else is a good practise */

 

/* click below link for alert dialog box */   
           }

For alert dialog box click below link

  http://www.testedcodes.net/2015/07/alert-dialog-box-1.html