Push Downstream Notification to Android App

[Dinesh Remje]

I am trying to push notification using gcm from my java code to the android app. Following is my code which i have done.

public String SendNotification(String message,ArrayList<String> regids) {
		String URLAddress = "https://android.googleapis.com/gcm/send";
	    String apiKey = "AIz*****************************";
	    String senderId = "7**********";
		String response = null;
		StringBuilder sb = new StringBuilder();
		String jsonRegids = null;
	    try 
	    {
	    	
	    	URL url = new URL(URLAddress);
			
	    	HttpURLConnection conn = (HttpURLConnection) url.openConnection();
	        conn.setRequestMethod("POST");
	        conn.setDoOutput(true);
			conn.setRequestProperty("Content-Type", "application/json");
			conn.setRequestProperty("Authorization", "key="+apiKey);
	        conn.setRequestProperty("Sender", "id="+senderId);
	        for(String fetch : regids) {
				if(jsonRegids != null)
	        		jsonRegids = jsonRegids+","+"\""+fetch;
	        	else
	        		jsonRegids = fetch+"\"";
	        }
	        
			String postData = "{\"collapse_key\":\"score_update\",\"time_to_live\":108,\"delay_while_idle\":true,\"data\": { \"message\" : " + "\"" + message + "\",\"time\": " + "\"" + System.currentTimeMillis() + "\"},\"registration_ids\":[\"" + jsonRegids + "\"]}";
			
			System.out.println(postData);
			
			OutputStream os = conn.getOutputStream();
			os.write(postData.getBytes());
			os.flush();
			
			BufferedReader br = new BufferedReader(new InputStreamReader(
					(conn.getInputStream())));
	 
			
			System.out.println("Output from Server with status code "+conn.getResponseCode());
			while ((response = br.readLine()) != null) {
				sb.append(response);
			}
	 
			conn.disconnect();
			br.close();
	 
	    } 
	    catch (MalformedURLException e) {
	    	sb.append("{\"error\":\"Internal server Error MalformedURLException\"}");
			e.printStackTrace();
	    } 
	    catch (UnknownHostException e) {
	    	sb.append("{\"error\":\"Internal server Error UnknownHostException\"}");
	    	e.printStackTrace();		
    	}
	    catch (IOException e) {
	    	sb.append("{\"error\":\"Internal server Error IOException\"}");
			e.printStackTrace();
	 	}
		return sb.toString();
	}

When I run this code I am getting the response as follows

{"multicast_id":9051968804510637573,"success":2,"failure":0,"canonical_ids":0,"results":[{"message_id":"0:1432287255854964%a62ca02566d6cf16"},{"message_id":"0:1432287255854962%a62ca02566d6cf16"}]}

But on the application I am not able to get any notification. What could be the problem.