Oops, I forgot about the second part of your question.
The visibility of interfaces across different packages is governed by the same rules that hold good for classes. For nested interfaces( interfaces defined within in classes, like in my example above, ) the enclosing class itself should be visible to the class that implements the interface. This means
you should first import the package that defines the enclosing class
and then use the dot resolution to reference the nested interface in the implements clause.
Ajith