PROPOSAL: Enhanced for each loop iteration control (original) (raw)

Stefan Schulz schulz at e-spirit.de
Mon Mar 30 15:03:30 PDT 2009

I don't particularly like the enriched for each iteration control. While the J5-for-each loop only adds as syntactic sugar for convenient looping, iteration control adds overhead to the loop by creating two instances per for-each, counting the index, etc. Hence, as a developer in most cases one would be better off with doing the iterator stuff oneself.

Frankly, I cannot see a great advantage of: for (Foo foo : fooList : it) { ... } saving two lines of code over: Iterator it = fooList.iterator(); while (it.hasNext()) { Foo foo = it.next(); ... } by adding two wrappers and stuff to the code in the background.

The idea to employ a label to access the iterator I find even worse. A label does not relate to anything at runtime but a location in code.

Stefan

Marek Kozieł schrieb:

As you can see i was thinking about it for while: http://mail.openjdk.java.net/pipermail/coin-dev/2009-March/001105.html

And i found few problems. New iterator Interface is wrong path, because people will be not able to use it with their iterators.

So from your proposal I would remove Interface-s and link iterator through label, label type is return type of .iterator() method. like: ArrayList some ....; ... i: for (Strign s:some){ if ( (s==null) || (s.equals("bad")) )) i.remove(); ... i.next(); // compile time error ? i.hasNext(); // OK Iterator s = i; // error i is not variable (it just allow to access it;) } String[] array ...; i: for (String s:array){ i.getIndex;//? }

-- Pozdrowionka. / Regards. Lasu aka Marek Kozieł http://lasu2string.blogspot.com/

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