Re: cloning Iterators?

Owen Jacobson <>
Mon, 18 Feb 2008 09:49:39 -0800 (PST)
On Feb 18, 9:46 am, Andreas Leitgeb <>

Mostly out of curiosity, and not so much out of any current real
need, I wonder, why Iterators are not cloneable.

I can't think of any reason, how this cloning could ever be non-
trivial to implement for any type of collection/iterator, but
perhaps someone else knows of some ferro concrete strong reasons
why this could be a bad idea, and cares to let me know?

By googling I found (from more than two years ago):


where two "solutions" (*) were suggested (by Patricia and Eric),
which both do not appear like satisfactory abstract solutions,
but rather workarounds for current non-cloneability.

* namely toArray() being one, and the other was: iterating the inner
loop from 0 to current element, rather than from current to end -
but how can I even detect, when two iterators sit on the the same
spot, if the collection had no uniqueness constraint in the first

As it stands, I can write (and have written) iterators over some input
source such as a stream or ResultSet. Forcing all Iterators to be
Clonable would make them unusable for that (and I'd basically end up
writing my own Iterator interface, sans Clonable).


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