After lots of try finally i got one solution and its work perfectly

Step 1 :Include two library.

compile 'com.squareup.okhttp3:okhttp:3.4.1'
compile 'com.google.firebase:firebase-messaging:9.2.0'

Step 2 : In your MainActivity or from where you want to send notifications.

OkHttpClient mClient = new OkHttpClient();

String refreshedToken = "";//add your user refresh tokens who are logged in with firebase.

JSONArray jsonArray = new JSONArray();
jsonArray.put(refreshedToken);

Step 3: Create one async task which sends notifications to all devices.

public void sendMessage(final JSONArray recipients, final String title, final String body, final String icon, final String message) {

        new AsyncTask<String, String, String>() {
            @Override
            protected String doInBackground(String... params) {
                try {
                    JSONObject root = new JSONObject();
                    JSONObject notification = new JSONObject();
                    notification.put("body", body);
                    notification.put("title", title);
                    notification.put("icon", icon);

                    JSONObject data = new JSONObject();
                    data.put("message", message);
                    root.put("notification", notification);
                    root.put("data", data);
                    root.put("registration_ids", recipients);

                    String result = postToFCM(root.toString());
                    Log.d("Main Activity", "Result: " + result);
                    return result;
                } catch (Exception ex) {
                    ex.printStackTrace();
                }
                return null;
            }

            @Override
            protected void onPostExecute(String result) {
                try {
                    JSONObject resultJson = new JSONObject(result);
                    int success, failure;
                    success = resultJson.getInt("success");
                    failure = resultJson.getInt("failure");
                    Toast.makeText(MainActivity.this, "Message Success: " + success + "Message Failed: " + failure, Toast.LENGTH_LONG).show();
                } catch (JSONException e) {
                    e.printStackTrace();
                    Toast.makeText(MainActivity.this, "Message Failed, Unknown error occurred.", Toast.LENGTH_LONG).show();
                }
            }
        }.execute();
    }

String postToFCM(String bodyString) throws IOException {



   public static final String FCM_MESSAGE_URL = "https://fcm.googleapis.com/fcm/send";
      final MediaType JSON
                = MediaType.parse("application/json; charset=utf-8");

        RequestBody body = RequestBody.create(JSON, bodyString);
        Request request = new Request.Builder()
                .url(Url.FCM_MESSAGE_URL)
                .post(body)
                .addHeader("Authorization", "key=" + "your server key")
                .build();
        Response response = mClient.newCall(request).execute();
        return response.body().string();
    }

Step 4 : Call in onclick of your button

    btnSend.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View v) {
            sendMessage(jsonArray,"Hello","How r u","Http:\google.com","My Name is Vishal");
        }
    });