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Need explain instanceof operator issue

matej spac

Joined: Apr 21, 2011
Posts: 28
I do not understand why instanceof operator is working as it is working. For example:

cause compilation error - this is clear, there is no IS-A relationship, Dog never ever could be a Cat.
But another example behaviour is weird for me:

works fine. It compiles and also run (and produce false of cource).
So tell me, in which universe Robot could be an Animal?
Why this don't cause compile error?

Paul Clapham

Joined: Oct 14, 2005
Posts: 19357

There could be a subclass of Robot which implements Animal. The compiler sees a variable of type Robot; this could be a reference to an instance of that subclass.

Try declaring the Robot class as "final" and see what changes.
matej spac

Joined: Apr 21, 2011
Posts: 28
wow, so briefly and so clearly :-)
thanks, now I understand
I agree. Here's the link:
subject: Need explain instanceof operator issue