Listener to notify the completion of a series of events(starting simultaneous services)
<p>I have three classes from which I start three services. These three services will be started simultaneously.</p>

<p>I have callback methods in each of these service class to know whether that particular service has been started.</p>

<p>There is no order in which what service out of these three would get started first, though they are started simultaneously.</p>

<p>Can someone please let me know the best approach to use in order that I am notified at the start of last service?</p>

<p>Any help is appreciated.</p>
