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https://issues.apache.org/jira/browse/COLLECTIONS-233?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel#action_12538725
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Brian Egge commented on COLLECTIONS-233:
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In some future version of Java, we may get Closures. It hasn't been voted into
7.0 yet. I think the Closures offered by the Collections is currently the
closest thing you can get in Java. True, it not a real closure like what you
get in Smalltalk or Ruby. Having learned to use Closures in Ruby, I found it
easy to pick up in the Collections framework. Having another name would make
the process more complex. If/when Java comes up with real closures, we could
depreciate the Closures interface, and give a good example of how to convert it
to a real one.
Introducing the Processor interface, would just create additional refactoring,
if the end goal is to use a built in Java mechanism instead.
I vote "won't fix" on this issue - at least not for now. Maybe if the 1.4
branch was in depreciated status, and there was a clear idea of if Closures are
going to be introduced into the Java languages, and if they are, what exactly
the usage is going to be. (As I understand there are two competing ways of
implementing closures).
> Closure is an inaccurate name
> -----------------------------
>
> Key: COLLECTIONS-233
> URL: https://issues.apache.org/jira/browse/COLLECTIONS-233
> Project: Commons Collections
> Issue Type: Improvement
> Components: Collection
> Reporter: Stephen Kestle
> Fix For: Generics
>
>
> The "Closure" in commons collections is not named well: for non-functional
> programmers it will induce a "what's that?", and for functional programmers
> it will confuse expectations.
>
> From http://en.wikipedia.org/wiki/Closure_(computer_science):
> A closure combines the code of a function with a special lexical environment
> bound to that function (scope).
>
> Java cannot pass functions, so the only way this can be done is with an
> (inner) class, as follows (also from wikipedia):
>
> class CalculationWindow extends JFrame {
> private JButton btnSave;
> ...
>
> public final calculateInSeparateThread(final URI uri) {
> // The expression "new Runnable() { ... }" is an anonymous class.
> Runnable runner = new Runnable() {
> void run() {
> // It can access final local variables:
> calculate(uri);
> // It can access private fields of the enclosing class:
> btnSave.setEnabled(true);
> }
> };
> new Thread(runner).start();
> }
> }
>
> Note how the Runnable accesses the btnSave variable in the function scope.
> This "special lexical environment" is NOT the same as passing a parameter
> through a constructor OR execute method. A Closure should NOT take a
> parameter for execute. It is not actually possible to have a "Closure"
> object, as that breaks the lexical environment.
>
> So, what to do?
>
> I would propose an interface called Processor. It is more intuitive and has
> many "real world" examples that can anchor the term so that it makes sense to
> the average programmer.
>
> For example, when applying for a passport, some documentation needs to be
> filled out, and then it will go through a process to get you a passport. You
> hand (or send) your forms to a clerk (Processor), and that's it. The
> Processor does not reply - the context that is passed in your form (your
> details) allows a message to be sent back at a later date.
>
> For backwards compatibility the interface would be
> public interface Processor<T> extends Closure<T>{}
> with the appropriate documentation. Closure would be deprecated with an
> appropriate explanation.
> However, it may be acceptable with the new version just to do a rename.
>
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