send notification based on json date

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Mobile

Android

My android app is a news app, and it connects to a web service to get JSON and shows it in a listView. News in app includes title, description, and the date time of the news. I want to get the latest JSON based on date time and if new JSON arrives with a later date time, I want to push a notification to the user.
how use this please help me
Api url sample:"http://api.khabarfarsi.net/api/news/top/1?tid=9&output=json[^]"

  @Override
		protected Void doInBackground(Void... arg0) {
			// Creating service handler class instance
			ServiceHandler sh = new ServiceHandler();

			// Making a request to url and getting response
			String jsonStr = sh.makeServiceCall(url, ServiceHandler.GET);

			Log.d("Response: ", "> " + jsonStr);

			if (jsonStr != null) {
				try {
					JSONObject jsonObj = new JSONObject(jsonStr);

					// Getting JSON Array node
					contacts = jsonObj.getJSONArray(TAG_ITEMS);
                                   
                                    // looping through All Contacts
					for (int i = 0; i < contacts.length(); i++) {
						JSONObject c = contacts.getJSONObject(i);

					String teaser = c.getString(TAG_TEASER);
				        String title = c.getString(TAG_TITLE);
                                        String date = c.getString(TAG_DATE);



						// tmp hashmap for single contact
						HashMap<string,> contact = new HashMap<string,>();

						// adding each child node to HashMap key => value
                                            contact.put(TAG_TEASER, teaser);
				            contact.put(TAG_TITLE, title);
                                            contact.put(TAG_DATE, date);
//
						// adding contact to contact list
						contactList.add(contact);
                                            
					}
				} catch (JSONException e) {
					e.printStackTrace();
				}
			} else {
				Log.e("ServiceHandler", "Couldn't get any data from the url");
			}

			return null;
		}