About Question enthuware.ocpjp.v7.2.1171 :

[Student]

What's wrong with a Queue? Isn't that an interface that allows non-unique objects in the order of insertion?

[admin]

I guess an argument can be made for Queue as well but Queue does not stipulate anything about the uniqueness of its elements. It depends on the implementation. You could have a valid Queue implementation that doesn't allow non unique elements.

While List API specifically says that it allows non unique elements.

HTH,
Paul.