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Re: Making one or more threads wait for another to produce a value or fail

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On Tue, 31 May 2011, markspace wrote:

> On 5/31/2011 7:00 AM, Tom Anderson wrote:
>
>> A blocking queue does synchronisation and delivers a value, but it only
>> delivers the value once - if the suitors all queue up on take(), only
>> the first will get the verdict.
>
> You could go around this by adding all threads to a list, and 
> interrupting all the ones to get the exceptional verdict.

Interruption doesn't quite line up with the exceptional verdict. 
Interruption is being told to stop waiting before there is a verdict; the 
exceptional verdict is learning that there won't be a verdict.

> Is there an values associated with the exceptional verdict?

Yes. Well, not the same kind as for a normal verdict, but there could be a 
reason, in the form of an exception.

> Also, what happens if a new suitor appears just as, or just after, the 
> widow delivers her verdict?  Do new or late suitors get the exceptional 
> verdict, or do they get queued up for some other process?

They get the same verdict as everyone else. Once the verdict is reached, 
it's set in stone.

> And lastly, are the verdicts immutable, in terms of being an immutable 
> Java object?  Can I just make a couple of objects (one verdict, one 
> exception) and hand them out to all and sundry?

Possibly. In my particular real case, yes. I'd be happy to leave that to 
the user of the mechanism.

This is where i've got to as of the end of today - hacked out and tidied, 
but not actually tested:

http://urchin.earth.li/~twic/Code/Promise.java

It's a simple implementation of a Future.

> It's the end of the month, and I'm packing to move.  I might not get 
> back to this thread for a couple of days.  In the meantime, good luck.

And to you!

tom

-- 
In Africa you can't walk in the countryside and think. You might be
eaten by a lion. -- AC Grayling

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Thread

Making one or more threads wait for another to produce a value or fail Tom Anderson <twic@urchin.earth.li> - 2011-05-31 15:00 +0100
  Re: Making one or more threads wait for another to produce a value or fail Peter Duniho <NpOeStPeAdM@NnOwSlPiAnMk.com> - 2011-05-31 07:14 -0700
    Re: Making one or more threads wait for another to produce a value or fail Tom Anderson <twic@urchin.earth.li> - 2011-05-31 16:46 +0100
      Re: Making one or more threads wait for another to produce a value or fail Deeyana <d.awlberg@hotmail.invalid> - 2011-05-31 19:23 +0000
        Re: Making one or more threads wait for another to produce a value or fail Tom Anderson <twic@urchin.earth.li> - 2011-06-01 22:12 +0100
      Re: Making one or more threads wait for another to produce a value or fail Peter Duniho <NpOeStPeAdM@NnOwSlPiAnMk.com> - 2011-05-31 20:45 -0700
        Re: Making one or more threads wait for another to produce a value or fail Patricia Shanahan <pats@acm.org> - 2011-05-31 21:37 -0700
          Re: Making one or more threads wait for another to produce a value or fail Peter Duniho <NpOeStPeAdM@NnOwSlPiAnMk.com> - 2011-06-01 07:18 -0700
            Re: Making one or more threads wait for another to produce a value or fail Patricia Shanahan <pats@acm.org> - 2011-06-01 09:01 -0700
        Re: Making one or more threads wait for another to produce a value or fail Lawrence D'Oliveiro <ldo@geek-central.gen.new_zealand> - 2011-06-01 16:40 +1200
          Re: Making one or more threads wait for another to produce a value or fail "John B. Matthews" <nospam@nospam.invalid> - 2011-06-01 11:22 -0400
            Re: Making one or more threads wait for another to produce a value or fail Lawrence D'Oliveiro <ldo@geek-central.gen.new_zealand> - 2011-06-02 10:15 +1200
              Re: Making one or more threads wait for another to produce a value or fail "John B. Matthews" <nospam@nospam.invalid> - 2011-06-01 21:38 -0400
        Re: Making one or more threads wait for another to produce a value or fail Tom Anderson <twic@urchin.earth.li> - 2011-06-01 22:07 +0100
          Re: Making one or more threads wait for another to produce a value or fail Peter Duniho <NpOeStPeAdM@NnOwSlPiAnMk.com> - 2011-06-01 22:46 -0700
  Re: Making one or more threads wait for another to produce a value or fail markspace <-@.> - 2011-05-31 08:26 -0700
    Re: Making one or more threads wait for another to produce a value or fail Tom Anderson <twic@urchin.earth.li> - 2011-05-31 19:13 +0100
  Re: Making one or more threads wait for another to produce a value or fail Patricia Shanahan <pats@acm.org> - 2011-05-31 09:06 -0700
    Re: Making one or more threads wait for another to produce a value or fail Paul Cager <paul.cager@googlemail.com> - 2011-05-31 10:08 -0700
      Re: Making one or more threads wait for another to produce a value or fail Patricia Shanahan <pats@acm.org> - 2011-05-31 10:39 -0700
        Re: Making one or more threads wait for another to produce a value or fail Paul Cager <paul.cager@googlemail.com> - 2011-05-31 16:24 -0700
  Re: Making one or more threads wait for another to produce a value or fail Lawrence D'Oliveiro <ldo@geek-central.gen.new_zealand> - 2011-06-01 12:33 +1200
    Re: Making one or more threads wait for another to produce a value or fail "John B. Matthews" <nospam@nospam.invalid> - 2011-06-01 00:38 -0400
  Re: Making one or more threads wait for another to produce a value or fail markspace <-@.> - 2011-06-02 14:10 -0700
    Re: Making one or more threads wait for another to produce a value or fail markspace <-@.> - 2011-06-02 14:25 -0700
    Re: Making one or more threads wait for another to produce a value or fail Patricia Shanahan <pats@acm.org> - 2011-06-02 14:43 -0700

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