title: check if a Json file is modified or new item is added programmatically
body: <p>I have a JSON file on my server with some data:</p>
  
  <p>This is some part of my JSON:</p>
  
  <pre><code>{
  "ringtones": [
      {
          "title": "Morning Alarm - Fur Elise",
          "link": "http://symphonyrecords.ir/rings/ala8_morning_alarm.mp3",
          "duration": "00:23",
          "id": 71,
          "genre": ["piano", "alarm"]
      },
      {
          "title": "Moein - Tolou",
          "link": "http://symphonyrecords.ir/rings/pia1_moein_tolou.mp3",
          "duration": "00:43",
          "id": 70,
          "genre": ["piano"]
      }
  
    ]
  }
  </code></pre>
  
  <p>I show this information in a list view, So first I download and save this JSON file in a temp folder, and then I populate my list with the downloaded file.</p>
  
  <p>This is how I get my JSON data</p>
  
  <pre><code>JSONArray jsonArray = jsonObj.getJSONArray("ringtones");
    for (int i = 0; i &lt; jsonArray.length(); i++) {
      JSONObject obj = jsonArray.getJSONObject(i);
  
      Product product = new Product();
      product.setTitle(obj.getString("title"));
      product.setThumbnailUrl(obj.getString("link"));
      product.setDuration(obj.getString("duration"));
      product.setId(obj.getInt("id"));
  
      JSONArray genreArray = obj.getJSONArray("genre");
      ArrayList&lt;String&gt; genre = new ArrayList&lt;&gt;();
      for (int j = 0; j &lt; genreArray.length(); j++) {
          genre.add((String) genreArray.get(j));
       }
  product.setGenre(genre);
  songList.add(product);
  </code></pre>
  
  <hr>
  
  <p>I don't want to push notification remotely|manually every time I add a new item in my JSON, So I need to programmatically check whenever a new item is added and show notification <strong><em>locally</em></strong>.</p>
  
  <p>I've prepared my notification method. but I have no idea how to do the check.</p>
  
  <p>Can you give me a hint, please?</p>