title: RxJava: How to to execute a task every 5 seconds only if the last task finished
body: <p>I'm using RxJava. I have to execute a specific task every 5 seconds. That works perfectly by using the "Observable.Interval" method.
  However, I also have the following constraint: A new task must not be executed if the last task didn't finished. In this case, the new task need to be executed only when the last one finished.</p>
  
  <p>I can't figure out how to do this simply with RxJava.</p>
  
  <p>All ideas would be really appreciated ^^</p>
  
  <p>Thanks for reading.</p>