title: When adding a object to a java collection is it added by value or reference?
body: <p>I've looked around and cannot figure this one out: I have a object that implemens an observer pattern and a List implementation that allows listeners to be added on the list whenever a change event is triggered on any object in the list to avoid manual add/remove listeners to each object int the list. </p>
  
  <p>The problem I have is when creating a new instance of the same List implementation and adding objects from existing lists the object changes are not getting triggered from beans added to the new list. My thought was that when adding an object to a Collection it just adds a pointer to the existing object which given this case the change notifications would be getting triggered on objects in the new list but this is not happening. Can anyone help me figure out what the problem might be? I have seen similar questions but none that can help me solve this problem. </p>
  
  <p>The use case, is a stock scanner where one list has all the stocks in the market I'm watching and the scanner list only has the stocks that pass the criteria but the scanner is not getting updates like price, volume etc that get triggered using the observation pattern. - Duncan </p>