Android : Use one service class for multiple notifications?

I have an app with multiple users, each user can start multiple counters for each activity they do ( run, sleep, reading...) to count how many seconds passed. Each counter will show time passed with a notification. This is sample code

Service class :

public class ExampleService extends Service {
    @Override
    public void onCreate() {
        super.onCreate();
    }
    @Override
    public int onStartCommand(Intent intent, int flags, int startId) {
        //String CHANNEL_ID="abc123";
        String input = intent.getStringExtra("inputExtra");
        Intent notificationIntent = new Intent(getApplicationContext(), MainActivity.class);
        PendingIntent pendingIntent = PendingIntent.getActivity(this,
                0, notificationIntent, 0);
        Notification notification = new NotificationCompat.Builder(this, CHANNEL_ID)
                .setContentTitle("Example Service")
                .setContentText(input)
                .setSmallIcon(R.drawable.icon_play)
                .setContentIntent(pendingIntent)
                .build();
        startForeground(100, notification);
        //do heavy work on a background thread
        //stopSelf();
        return START_STICKY;
    }
    @Override
    public void onDestroy() {
        super.onDestroy();
    }
    @Nullable
    @Override
    public IBinder onBind(Intent intent) {
        return null;
    }
}

Main activity: Call startService() to start the service and the notification Call stopService() to stop the service and the notification

public void startService(View v) {
    String input = editTextInput.getText().toString();
    Intent serviceIntent = new Intent(this, ExampleService.class);
    serviceIntent.putExtra("inputExtra", input);
    ContextCompat.startForegroundService(this, serviceIntent);
}
public void stopService(View v) {
    Intent serviceIntent = new Intent(this, ExampleService.class);
    stopService(serviceIntent);
}

Each notification work independently, the user can stop one activity by clicking on the stop button on a notification while the other notifications are still running.

If I use one Service class for each activity, it works, but it is impossible to add more service classes when I add a new user. **

If I use only one Service class for all notifications, when I call stopService(), all the notifications will be destroyed.

**

Is there any solution to use ONLY ONE Service class for ALL NOTIFICATIONS and users can control each notification INDEPENDENTLY???