Class Cast Exception

[Rhea Rhea]

Hi,
I am trying to cast a Collection to a LinkedList.Is that possible? At Compile time I am fine but at runtime my code returns a Class Cast Exception at this line :
******************************************
LinkedList acadList = new LinkedList();
acadList = (LinkedList)acadClassHome.findOpenClasses(); --ClassCastException
// findOpenClasses() returns a Collection of objects.
********************************************
The findOpenClasses is actually in an EJB which returns a Collection of objects.
What can I do to get back a LinkedList from a Collection.
Thanks,

[Mike Gershman]

If you want to convert an arbitrary Collection object into a LinkedList, you can do:
LinkedList acadList = new LinkedList( acadClassHome.findOpenClasses() );

[David Harkness]

The compiler allows it because, at runtime, the returned Collection could theoretically be a LinkedList (or a TreeMap, or a Stack, or ...). You get a ClassCastException because, at runtime, it turns out the returned Collection is not a LinkedList (or a subclass of it). If you'd like to see what it is, try this:

System.out.println(acadClassHome.findOpenClasses().getClass().getName());

However, I suggest that you back up a step and think about what you're doing. Do you need to operate on the Collection as a LinkedList? If so, Mike's code will do that.

Or do you just need the List methods (indexed access)? If so, you can cast it to the interface List. Coding to interfaces, especially with the Collections classes, is much cleaner and allows you to switch the particular implementation (ArrayList for LinkedList) without changing your code.

[Rhea Rhea]

Mike and David,
I tried out Mike's Suggestion and it worked,Thanks.I do need to use the Collection as a LinkedList as the caller of the method needs a LL returned.
Thanks again.
Rhea