On 23/02/2012 10:41 PM, Doug Lea wrote:
On 02/22/12 21:44, David Holmes wrote:
I'm not a fan of collections containing themselves, but I think it is
simple to fix contains(o)/contains[Key]|[Value](o) and remove(o) in a similar
way. Though none of the wrapped collections currently handle that case, so I'm
okay with not addressing this part.
It was a deliberate decision not to include any evasive schemes
for collections that contain themselves, because the problem is
unsolvable in general. The patch addresses those that directly contain
themselves, but not the transitive closure, as in:
c1 contains c2 that in turn contains c1. Our take was that
it is a feature, not a bug, that anyone using equals or hashCode
in such cases hits infinite recursion.
I must confess that I had misunderstood the basic issue here and thought
that there was a problem independent of self-containment.
That said, an equals method that checks for o==this is pretty normal
(and recommended by Effective Java Item 7) and we at least now have
consistency amongst the wrapper classes. I'll add a note to the CR to
that effect.
Michael: good to go (if it hasn't already)
Thanks,
David
People are free to change policies about this, but do bear in
mind that any changes along these lines are intrinsically
incomplete.
(Although for pre-collections (Java1.1) legacy
compatibility reasons, java.util.Hashtable.hashCode does
include an ugly stopgap to avoid infinite recursion
in the direct case.)
-Doug
