Am 05.05.2015 um 19:44 schrieb Benedikt Ritter: > 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 >
ISTR that also Bloch in "Effective Java" recommended the approach of passing in a zero-length array (which can be a constant as it is immutable) and let the method create a properly sized array itself. Oliver > >> >> Cheers, >> Jörg >> >> >> --------------------------------------------------------------------- >> To unsubscribe, e-mail: dev-unsubscr...@commons.apache.org >> For additional commands, e-mail: dev-h...@commons.apache.org >> >> > > --------------------------------------------------------------------- To unsubscribe, e-mail: dev-unsubscr...@commons.apache.org For additional commands, e-mail: dev-h...@commons.apache.org
