StackOverflowError with self-relations using Java collections

[pereirazc]

The Drools runtime throws StackOverflowError when a self-relation scenario (bellow) happens

The self-relation friends causes a loop when the engine calls toStringfor the List class because in a situation of Friendship between A and B, A is inside of B's friends and vice-versa.

declare Person
    id: int
    name: String
    friends: List
end

declare Friendship extends Situation
    friendA: Person @part(label = "a")
    friendB: Person @part(label = "b")
end

rule Friendship
@role(situation)
@type(Friendship)
 when
    a: Person()
    b: Person(this != a)
 then
    SituationHelper.situationDetected(drools);
 end

The problem is AbstractCollection's toString method, a quick solution would be to offer our own List class reimplementing toString.