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From Benedikt Ritter <brit...@apache.org>
Subject Re: [lang] Allocate array of the correct size
Date Tue, 05 May 2015 17:07:20 GMT
2015-05-05 17:51 GMT+02:00 Jörg Schaible <joerg.schaible@swisspost.com>:

> Hi Benedikt,
>
> Benedikt Ritter wrote:
>
> > 2015-05-05 14:52 GMT+02:00 Benedikt Ritter <britter@apache.org>:
> >
> >> Hello Jörg,
> >>
> >> 2015-05-05 8:30 GMT+02:00 Jörg Schaible <joerg.schaible@swisspost.com>:
> >>
> >>> Hi Benedikt,
> >>>
> >>> britter@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 <britter@apache.org>
> >>> > Authored: Mon May 4 21:26:07 2015 +0200
> >>> > Committer: Benedikt Ritter
> >>> > <britter@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?

Benedikt


>
> Cheers,
> Jörg
>
>
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-- 
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