title: Observing multiple observables while avoiding instanceof operator in java?
body: <p>If I have an object that I want to be able to observe several other observable objects, not all of the same type. For example I want A to be able to observe B and C. B and C are totally un-related, except for the fact that they both implement Observable.</p>
  
  <p>The obvious solution is just to use "if instanceof" inside the update method but that quickly can become messy and as such I am wondering if there is another way?</p>