How to find the item ID of a list in SharePoint using REST?

At some point in time, I want to update a specific Item in a list.

I Know that I have to use the REST call to update a specific item. Below is my URL.'ClockTrack')/items(5) 

items(5)” I have hard coded the item ID.

My question is how do I get that ID “items(5)” of a specific Item from a list.

I have a Scenario where I will inserting an Item to a few fields and later I’ll be updating that Item with additional data.

my code for inserting data to list.

 public void insertDataItems() {      try {         CookieManager cookieManager = (CookieManager)CookieHandler.getDefault();         cookies = cookieManager.getCookieStore().getCookies();        // String body ="{ '__metadata': { 'type': 'SP.Data.ClockTrackListItem' },'UId' : '171028', 'CurrentDate' : '2016-08-05T04:00:00Z' ," +        //         "'TimeIn' : '10:12:12' , 'TimeOut': '22:12:12' ,'TotalTime': '10:12:12' ,'Title': 'Dharma'}";         String body ="{ '__metadata': { 'type': 'SP.Data.ClockTrackListItem' },'UId': '32156','TimeIn' : '06:00:00' , 'TimeOut': '08:00:00' ,'TotalTime': '02:00:00'}";           Uri uri = Uri.parse("'ClockTrack')/items(5)");         URL url = new URL(uri.toString());         HttpURLConnection urlConnection = (HttpURLConnection) url.openConnection();         urlConnection.setDoInput (true);         urlConnection.setDoOutput(true);         urlConnection.setRequestMethod("POST");         urlConnection.setRequestProperty("Accept", "application/json;odata=verbose");         urlConnection.setRequestProperty("content-type", "application/json;odata=verbose");         urlConnection.setRequestProperty("X-RequestDigest",getRequestDigest());         urlConnection.setRequestProperty("X-HTTP-Method","MERGE");         urlConnection.setRequestProperty("IF-MATCH","*");          urlConnection.connect();         OutputStream os = urlConnection.getOutputStream();         os.write(body.getBytes());         os.flush();         os.close();         int resCode = urlConnection.getResponseCode();         Log.d("Response Code :" ," "+resCode);         InputStream inputStream = urlConnection.getInputStream();         BufferedReader reader =new BufferedReader(new InputStreamReader((inputStream)));         StringBuffer buffer = new StringBuffer();         String line;         while((line = reader.readLine()) != null)         {             buffer.append(line + "\n");         }         String restResult = buffer.toString();         Log.d("----Buffer String-----:" , restResult);         JSONObject jobj = new JSONObject(restResult).getJSONObject("d");     }     catch (Exception e)     {         Log.v("Retrieve List", e.toString());         e.printStackTrace();     }  }