android - Retrieve data from Google Books Api -

i'm new android , using web apis, , i'm writing android app scans barcode book , search isbn in google books api.

i have url after barcode scan: https://www.googleapis.com/books/v1/volumes?q=isbn:9788432250651&aizasycpyez5556x4uzpv6rf4kkspj9dscs_q_c

and next code:

private class getbookinfo extends asynctask <view, void, integer> {          @override         protected integer doinbackground(view... urls) {             // make call url             makecall("https://www.googleapis.com/books/v1/volumes?" +                     "q=isbn:" + ean_content + "&aizasycpyez5556x4uzpv6rf4kkspj9dscs_q_c");              //print call in console             system.out.println("https://www.googleapis.com/books/v1/volumes?" +                     "q=isbn:" + ean_content + "&aizasycpyez5556x4uzpv6rf4kkspj9dscs_q_c");              return null;         }           @override         protected void onpreexecute() {             // can start progress bar here         }          @override         protected void onpostexecute(integer result) {              string ruta = save_cover(getapplicationcontext(), title, book_cover);              intent intent = new intent(mainactivity.this, spreadsheets.class); //            intent.putextra(title,title); //            intent.putextra(author,authors); //            intent.putextra(date,date); //            intent.putextra(category,categories); //            intent.putextra(description,description);             //finish();             startactivity(intent);             finish();          }     }      public void makecall(string stringurl) {          url url = null;         bufferedinputstream = null;         jsonreader jsonreader;          try {             url = new url(stringurl);         } catch (exception ex) {             system.out.println("malformed url");         }          try {             if (url != null) {                 httpsurlconnection urlconnection = (httpsurlconnection) url.openconnection();                 = new bufferedinputstream(urlconnection.getinputstream());             }         } catch (ioexception ioe) {             system.out.println("ioexception");         }          if (is != null) {             try {                 jsonreader = new jsonreader(new inputstreamreader(is, "utf-8"));                 jsonreader.beginobject();                 while (jsonreader.hasnext()) {                     string name = jsonreader.nextname();                      if (name.equals("title")) {                         title = jsonreader.nextstring();                     }                     else if (name.equals("authors")) {                         authors = jsonreader.nextstring();                     }                     else if (name.equals("publisheddate")) {                        date = jsonreader.nextstring();                     }                     else if (name.equals("categories")) {                         categories = jsonreader.nextstring();                     }                     else if (name.equals("description")) {                         description = jsonreader.nextstring();                     } //                    else if (name.equals("averagerating")) { //                        rating = jsonreader.nextstring(); //                    }                     else if (name.equals("thumbnail")) {                         image = jsonreader.nextstring();                         book_cover = download_cover(image);                     }                     else {                         jsonreader.skipvalue();                     }                 }                 jsonreader.endobject();             }              catch (exception e) {                 system.out.println("exception");             }          }     } 

this isn't retrieving api. appreciate help, thank you!

i think need next request connection api, open connection, using json retrieve data api , use inputstream data stored in array. :implement these methods in class:

private static string makehttprequest(url url) throws ioexception

private static string readfromstream(inputstream inputstream) throws ioexception

private static list extractfeaturefromjson(string booksjson)

public static list featchbookdata(string requesturl)