title: service onStartCommand method
body: <p>I was wondering if two different threads calls <code>startService</code> on service <code>A</code> at the same time, does the service execute <code>onStartCommand()</code> for <strong>both of them separately or does one cancel the other</strong>? </p>
  
  <p>I want to understand services in <code>Android</code>.</p>