How can I defined the class in ice?

HI,
if i have two classes (A and which are many to many .how can I defined them?
Class A{
private long id;
private Set<B> agentGroups = new HashSet<B>(0)
}
Class B{
private long id;
private Set<A> agents = new HashSet<A>(0);
}

I use java and ice3.4.1

The equivalent Slice definitions would be something like:

module Demo
{

class A;
class B;

sequence<A> ASeq;
sequence<B> BSeq;

class A
{
   long id;
   BSeq agentGroups;
};

class B
{
  long id;
  ASeq agents;
};

};

Best regards,
Bernard

thank you！