Re: List or Iterator

"Mike Schilling" <>
Sun, 26 Jul 2009 15:01:33 -0700
Tom Anderson wrote:

On Sat, 25 Jul 2009, Mike Schilling wrote:

Lew wrote:

Roedy Green wrote:

Iterator is more general. You could for example later modify the
producer to fetch records from a sequential file, without having
change the client.

The general rule is avoid giving your client any more power than
they absolutely need to get the job done.

I guess you're focusing on returning an Iterator, as opposed to
passing one in as an argument.

In the argument scenario you need more work to avoid the
modification issues other respondents have mentioned.

Even in the return scenario, you might get more joy returning an
Iterable than an Iterator.

Like most of these questions, it depends on what you're really
If you're passing something that can be iterated over more than
(e.g. the children of a DOM Node), pass Iterable. If it can only
iterated over once and then it's gone (e.g. a series of SAX events
generated from an InputStream), pass Iterator.

You can probably tell that I've been doing a lot of XML programming

Do you have a way of getting an Iterable interface in the mix here
somewhere? I had a related, although simpler, problem recently, and
was very happy to be able to work an Iterable in, because i could
for-loop over it. If a DOM node can be iterated in several ways, it
can't be Iterable itself, but could you have its getChildren etc
methods return some sort of NodeSequence object which, while not
necessarily a full-blown List, was Iterable? Is there any reasonable
way to combine this with one-shotness?

We've got quite a bit of infrastructure built around DOMs. It
predates Iterable, but includes what amounts to an Iterator that
reutnrs only the children of an Element that are themselves Elements.
(It predates generics as well, so making it a real Iterator was less
useful than making it return Elements rather than Objects that need to
be cast.) Building something similar on top of SAX or better yet STAX
wouldn't be difficult.

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