generators in Java?

[Tom Sheffler]

This may have been discussed before, so I apologize.

Does Java have generators? I am aware of the "Iterator" interface,
but it seems much more restrictive. Python generators are useful
for many more things than simply list enumeration, but the Java
Iterator seems limited.

Tom

[Diez B. Roggisch]

Re: generators in Java?

Tom Sheffler schrieb:[color=blue]
>
> This may have been discussed before, so I apologize.
>
> Does Java have generators? I am aware of the "Iterator" interface,
> but it seems much more restrictive. Python generators are useful
> for many more things than simply list enumeration, but the Java
> Iterator seems limited.[/color]

No, it hasn't. One thing people do is to create threads that communicate
via a queue and block while that queue has an item in it. But of course
that comes at additional overhead of thread context switching.


Regards,

Diez

[Dave Benjamin]

Re: generators in Java?

On Fri, 30 Dec 2005, Tom Sheffler wrote:
[color=blue]
> Does Java have generators? I am aware of the "Iterator" interface,
> but it seems much more restrictive. Python generators are useful
> for many more things than simply list enumeration, but the Java
> Iterator seems limited.[/color]

What makes you think that Java's Iterators are more restrictive or
limited? As far as I understand, Java's hasNext/next protocol is
essentially the same as Python's next/StopIteration protocol. The main
advantage of the use of generators is that, when converting from a
callback-style or non-streaming function to one that produces values
on-demand, you don't have to rewrite your function to save intermediate
states (which can be a considerable amount of work).

A good explanation of the rationale for generators in Python is in the
"Motivation " section of PEP 255:

http://www.python.org/peps/pep-0255.html

--
.:[ dave benjamin: ramen/[spoomusic.com] ]:.