Practical side of the ability to define a class within an interface in Java?

Question

What would be the practical side of the ability to define a class within an interface in Java:

interface IFoo
{
    class Bar
    {
        void foobar (         


        

Answer 1

I guess you could define a class that is used as the return type or parameter type for methods within the interface. Doesn't seem particularly useful. You might as well just define the class separately. The only possible advantage is that it declares the class as "belonging" to the interface in some sense.