c.toArray might (incorrectly) not return Object[] (see 6260652) (original) (raw)

Martin Buchholz martinrb at google.com
Mon May 25 06:42:47 UTC 2009

I continue to believe that not fixing 6260652 was a mistake, both technically and from the point of view of community relations.

I prefer the current implementation of ArrayList(Collection) to one using c.toArray(ZERO_ARRAY) because it has slightly less trust of the argument collection. (In any case, I think it's an academic question; it would not be worth changing either implementation to the other for aesthetic reasons)

Historically, we have also had bugs implementing toArray(T[]).

Martin

On Fri, May 22, 2009 at 05:05, David Holmes - Sun Microsystems < David.Holmes at sun.com> wrote:

Doug Lea said the following on 05/22/09 21:56:

Sorry; I should have been clearer about why c.toArray(new Object[c.size()]) is subtly wrong here. ArrayList.size must equal the number of elements, which might be different than the array size. If c's size shrinks at an inconvenient moment during the call, then we might think that the trailing null, that toArray(T[] a) is required to append if a is too big, is actually a (null) element of the collection.

Ah I see. I'm thinking though that I'd find this hack more aesthetically pleasing: static final Object[] ZEROARRAY = new Object[0]; ... elementData = c.toArray(ZEROARRAY); this deals with the size issue, gets the right type and only creates one array (asuming the collection doesn't concurrently grow). Cheers, David -------------- next part -------------- An HTML attachment was scrubbed... URL: <http://mail.openjdk.java.net/pipermail/core-libs-dev/attachments/20090524/7979cb8d/attachment.html>

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