2015-05-05 19:13 GMT+02:00 Jörg Schaible <joerg.schai...@gmx.de>: > Benedikt Ritter wrote: > > > 2015-05-05 17:51 GMT+02:00 Jörg Schaible <joerg.schai...@swisspost.com>: > > > >> Hi Benedikt, > >> > >> Benedikt Ritter wrote: > >> > >> > 2015-05-05 14:52 GMT+02:00 Benedikt Ritter <brit...@apache.org>: > >> > > >> >> Hello Jörg, > >> >> > >> >> 2015-05-05 8:30 GMT+02:00 Jörg Schaible > >> >> <joerg.schai...@swisspost.com>: > >> >> > >> >>> Hi Benedikt, > >> >>> > >> >>> brit...@apache.org wrote: > >> >>> > >> >>> > Repository: commons-lang > >> >>> > Updated Branches: > >> >>> > refs/heads/master 8548b12d8 -> 60b32953a > >> >>> > > >> >>> > > >> >>> > Allocate array of the correct size > >> >>> > > >> >>> > > >> >>> > Project: http://git-wip-us.apache.org/repos/asf/commons-lang/repo > >> >>> > Commit: > >> >>> > > http://git-wip-us.apache.org/repos/asf/commons-lang/commit/60b32953 > >> >>> Tree: > >> >>> > http://git-wip-us.apache.org/repos/asf/commons-lang/tree/60b32953 > >> >>> > Diff: > >> >>> > http://git-wip-us.apache.org/repos/asf/commons-lang/diff/60b32953 > >> >>> > > >> >>> > Branch: refs/heads/master > >> >>> > Commit: 60b32953a968e5623f82a6b27d6c679bc17c48e5 > >> >>> > Parents: 8548b12 > >> >>> > Author: Benedikt Ritter <brit...@apache.org> > >> >>> > Authored: Mon May 4 21:26:07 2015 +0200 > >> >>> > Committer: Benedikt Ritter > >> >>> > <brit...@apache.org> Committed: Mon May 4 > >> >>> > 21:26:07 2015 +0200 > >> >>> > > >> >>> > > >> ---------------------------------------------------------------------- > >> >>> > .../apache/commons/lang3/builder/ReflectionToStringBuilder.java > >> >>> > | 2 > >> >>> +- > >> >>> > 1 file changed, 1 insertion(+), 1 deletion(-) > >> >>> > > >> ---------------------------------------------------------------------- > >> >>> > > >> >>> > > >> >>> > > >> >>> > >> > http://git-wip-us.apache.org/repos/asf/commons-lang/blob/60b32953/src/main/java/org/apache/commons/lang3/builder/ReflectionToStringBuilder.java > >> >>> > > >> ---------------------------------------------------------------------- > >> >>> > diff --git > >> >>> > > >> >>> > >> >>> > >> > >> > > a/src/main/java/org/apache/commons/lang3/builder/ReflectionToStringBuilder.java > >> >>> > > >> >>> > >> >>> > >> > >> > > b/src/main/java/org/apache/commons/lang3/builder/ReflectionToStringBuilder.java > >> >>> > index 5904469..7a78170 100644 --- > >> >>> > > >> >>> > >> >>> > >> > >> > > a/src/main/java/org/apache/commons/lang3/builder/ReflectionToStringBuilder.java > >> >>> > +++ > >> >>> > > >> >>> > >> >>> > >> > >> > > b/src/main/java/org/apache/commons/lang3/builder/ReflectionToStringBuilder.java > >> >>> > @@ -333,7 +333,7 @@ public class ReflectionToStringBuilder extends > >> >>> > ToStringBuilder { > >> >>> > list.add(e.toString()); > >> >>> > } > >> >>> > } > >> >>> > - return list.toArray(ArrayUtils.EMPTY_STRING_ARRAY); > >> >>> > + return list.toArray(new String[list.size()]); > >> >>> > } > >> >>> > >> >>> What's the benefit of this? Where's the difference by letting > >> >>> List.toArray() > >> >>> allocate the appropriate array compared to do it on your own? > >> >>> ArrayUtils.EMPTY_STRING is a constant after all, so there's no > >> >>> additional allocation. > >> >>> > >> >> > >> >> I changed this because my IDE complained about that line of code: > >> >> > >> >> "Call to 'toArray' with zero-length array argument > >> >> 'ArrayUtils.EMPTY_STRING_ARRAY' > >> >> > >> >> Reports any call to 'toArray' on an object or type or subtype of > >> >> java.util.Collection with a zero-length argument. When passing an > >> >> array of too small size, the toArray() method has to construct a new > >> >> array of the correct size using reflection. This has significantly > >> >> worse performance than passing in an array of at least the size of > the > >> >> collection itself." > >> >> > >> >> To be honest, I did not do any performance benchmarks to make sure > >> >> this is really true. > >> >> > >> > > >> > In any case, the commit message should have been more explanatory. > >> > Sorry about that. > >> > >> Well, that warning is somewhat stupid, if you're using a constant for > the > >> zero length array. The "worse performance" only occurs if you provide a > >> new array instance that is too small. > >> > > > > ... which will always be the case unless the list is empty, or am I > > missing something here? > > Where's the difference in creating a new array of proper size yourself or > let the method do it? It's even worse now, because now you create a new > instance *even* if the list is empty. >
The difference is, that toArray(T[]) will have to create a new instance using reflection every time the ReflectionToStringBuilder.toNoNullStringArray(Object[]) method is invoked with an non empty array (see ArrayList.toArray(T[]), line 389). The IDE report complains that this will be significantly slower then creating a new array of the correct type and size using an array constructor. As I said, I haven't done any benchmarks. But it seemed logical to me. br, Benedikt > > Cheers, > Jörg > > > --------------------------------------------------------------------- > To unsubscribe, e-mail: dev-unsubscr...@commons.apache.org > For additional commands, e-mail: dev-h...@commons.apache.org > > -- http://people.apache.org/~britter/ http://www.systemoutprintln.de/ http://twitter.com/BenediktRitter http://github.com/britter
