Re: Java-Swarm questions

[Ralf Stephan]

Paul E. Johnson wrote 
> 2. This one thing in Java really goes against my C impulse.  Suppose you
> want to interate over a collection several times. You create an
> iterator, step through the collection.  There is (apparently??) no way
> to tell the Java iterator to go back to the beginning of the collection,
> so the only thing to do is to create another one?  And you don't drop
> the first one? 

That is collected by GC, at some time, yes.  In (Obj)-C, you keep the
the control over *when* space is freed, with the drawback of
additional work/risk.

> 
> 
>    public void stepAgents (){
>         int x;
>         Iterator iterator = agents.listIterator(0);
>         Agent anAgent = null ;
>         while (iterator.hasNext()){
>             anAgent = (Agent) iterator.next();
>             x = anAgent.makeChoice();
>         }
> 
>         iterator = agents.listIterator(0);
>         while (iterator.hasNext()){
>             anAgent = (Agent) iterator2.next();
>             anAgent.updateStrategies();
>         }
>     }
> 
> 
> There's no way to drop the first iterator forcefully, before coining the
> second?  Aren't we relying on the garbage collector for an awful lot of
> help?  

Yes, but it works, with the disadvantage of losing fine-grained control
over *when* space is freed.  But Sun succeded in getting back some 
detail with Java 1.2 AFAIR, where additional GC flags were introduced.



ralf

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