I wonder where this should be documented. We could add a // comment to each call site, that seems the simplest. Adding a package or component level documentation in the style guideline for example could easily be overlooked by someone in a debugger for example. So each call site would be best IMO something like // Using an empty array can be faster I don't really want a link to an external random blog in the source.
Thoughts? Then we can consider doing it throughout Commons. Gary On Fri, Dec 27, 2019 at 7:23 AM Pascal Schumacher <pascalschumac...@gmx.net> wrote: > Feel free to revert the changes. > > I would revert my changes, but Garry did some follow-up changes so these > would to be reverted first. > > Am 27.12.2019 um 12:33 schrieb sebb: > > As that article says in conclusion, T[0] seems currently faster, but that > > may not always be the case with future VMs. > > > > Also it says that IntelliJ IDEA and PMD recommend using T[size] rather > than > > T[0]. > > If we release code with T[0], I suspect we will get complaints that the > > code is not efficient according to x, y and z. > > > > I'm not convinced that the change is worth it, but if it is agreed the > code > > must be thoroughly documented to try and forestall complaints. > > According to the article, using a constant empty array is faster, but > only > > marginally. If there is a constant available it would probably make sense > > to use it. > > This should also be documented, as it affects the return value for the > > empty case. > > > > S. > > On Fri, 27 Dec 2019 at 09:28, Pascal Schumacher < > pascalschumac...@gmx.net> > > wrote: > > > >> see https://shipilev.net/blog/2016/arrays-wisdom-ancients/ > >> > >> Am 27.12.2019 um 01:24 schrieb sebb: > >>> Also, where is it documented that modern JVMs are faster? > >>> To which JVMs does this apply? > >>> > >>> S. > >>> > >>> On Thu, 26 Dec 2019 at 22:08, Gary Gregory <garydgreg...@gmail.com> > >> wrote: > >>>> Please do not cause garbage to apparently be generated all over the > >> place > >>>> by creating new empty arrays all the time. Use the constants Commons > >> Lang > >>>> constants already defines; see ArrayUtils. > >>>> > >>>> Gary > >>>> > >>>> On Thu, Dec 26, 2019 at 4:48 PM <pascalschumac...@apache.org> wrote: > >>>> > >>>>> This is an automated email from the ASF dual-hosted git repository. > >>>>> > >>>>> pascalschumacher pushed a commit to branch master > >>>>> in repository https://gitbox.apache.org/repos/asf/commons-lang.git > >>>>> > >>>>> > >>>>> The following commit(s) were added to refs/heads/master by this push: > >>>>> new 84668a2 Use Collection#toArray(new T[0]) instead of a > >> presized > >>>>> array as it is faster on modern JVMs. > >>>>> 84668a2 is described below > >>>>> > >>>>> commit 84668a2d980316a580030fd64764cb072b520b09 > >>>>> Author: pascalschumacher <pascalschumac...@gmx.net> > >>>>> AuthorDate: Thu Dec 26 22:48:12 2019 +0100 > >>>>> > >>>>> Use Collection#toArray(new T[0]) instead of a presized array as > >> it is > >>>>> faster on modern JVMs. > >>>>> --- > >>>>> src/main/java/org/apache/commons/lang3/CharSet.java | > 2 > >> +- > >>>>> src/main/java/org/apache/commons/lang3/StringUtils.java | > 10 > >>>>> +++++----- > >>>>> .../org/apache/commons/lang3/exception/ExceptionUtils.java | > 6 > >>>> +++--- > >>>>> src/main/java/org/apache/commons/lang3/reflect/FieldUtils.java | > 4 > >> ++-- > >>>>> .../java/org/apache/commons/lang3/reflect/MethodUtils.java | > 2 > >> +- > >>>>> src/main/java/org/apache/commons/lang3/reflect/TypeUtils.java | > 2 > >> +- > >>>>> src/main/java/org/apache/commons/lang3/text/StrTokenizer.java | > 4 > >> ++-- > >>>>> .../org/apache/commons/lang3/time/DurationFormatUtils.java | > 2 > >> +- > >>>>> .../java/org/apache/commons/lang3/time/FastDatePrinter.java | > 2 > >> +- > >>>>> .../commons/lang3/concurrent/EventCountCircuitBreakerTest.java | > 2 > >> +- > >>>>> 10 files changed, 18 insertions(+), 18 deletions(-) > >>>>> > >>>>> diff --git a/src/main/java/org/apache/commons/lang3/CharSet.java > >>>>> b/src/main/java/org/apache/commons/lang3/CharSet.java > >>>>> index 3fdfd07..7955115 100644 > >>>>> --- a/src/main/java/org/apache/commons/lang3/CharSet.java > >>>>> +++ b/src/main/java/org/apache/commons/lang3/CharSet.java > >>>>> @@ -225,7 +225,7 @@ public class CharSet implements Serializable { > >>>>> // NOTE: This is no longer public as CharRange is no longer a > public > >>>>> class. > >>>>> // It may be replaced when CharSet moves to Range. > >>>>> /*public*/ CharRange[] getCharRanges() { > >>>>> - return set.toArray(new CharRange[set.size()]); > >>>>> + return set.toArray(new CharRange[0]); > >>>>> } > >>>>> > >>>>> > >>>>> > >> > //----------------------------------------------------------------------- > >>>>> diff --git a/src/main/java/org/apache/commons/lang3/StringUtils.java > >>>>> b/src/main/java/org/apache/commons/lang3/StringUtils.java > >>>>> index abde7ec..d629806 100644 > >>>>> --- a/src/main/java/org/apache/commons/lang3/StringUtils.java > >>>>> +++ b/src/main/java/org/apache/commons/lang3/StringUtils.java > >>>>> @@ -7507,7 +7507,7 @@ public class StringUtils { > >>>>> currentType = type; > >>>>> } > >>>>> list.add(new String(c, tokenStart, c.length - > tokenStart)); > >>>>> - return list.toArray(new String[list.size()]); > >>>>> + return list.toArray(new String[0]); > >>>>> } > >>>>> > >>>>> /** > >>>>> @@ -7735,7 +7735,7 @@ public class StringUtils { > >>>>> } > >>>>> } > >>>>> > >>>>> - return substrings.toArray(new String[substrings.size()]); > >>>>> + return substrings.toArray(new String[0]); > >>>>> } > >>>>> > >>>>> // > >>>>> > ----------------------------------------------------------------------- > >>>>> @@ -7923,7 +7923,7 @@ public class StringUtils { > >>>>> if (match || preserveAllTokens && lastMatch) { > >>>>> list.add(str.substring(start, i)); > >>>>> } > >>>>> - return list.toArray(new String[list.size()]); > >>>>> + return list.toArray(new String[0]); > >>>>> } > >>>>> > >>>>> /** > >>>>> @@ -8022,7 +8022,7 @@ public class StringUtils { > >>>>> if (match || preserveAllTokens && lastMatch) { > >>>>> list.add(str.substring(start, i)); > >>>>> } > >>>>> - return list.toArray(new String[list.size()]); > >>>>> + return list.toArray(new String[0]); > >>>>> } > >>>>> > >>>>> /** > >>>>> @@ -8835,7 +8835,7 @@ public class StringUtils { > >>>>> if (list.isEmpty()) { > >>>>> return null; > >>>>> } > >>>>> - return list.toArray(new String[list.size()]); > >>>>> + return list.toArray(new String[0]); > >>>>> } > >>>>> > >>>>> /** > >>>>> diff --git > >>>>> > a/src/main/java/org/apache/commons/lang3/exception/ExceptionUtils.java > >>>>> > b/src/main/java/org/apache/commons/lang3/exception/ExceptionUtils.java > >>>>> index 5969614..dd154e3 100644 > >>>>> --- > >>>> a/src/main/java/org/apache/commons/lang3/exception/ExceptionUtils.java > >>>>> +++ > >>>> b/src/main/java/org/apache/commons/lang3/exception/ExceptionUtils.java > >>>>> @@ -274,7 +274,7 @@ public class ExceptionUtils { > >>>>> } > >>>>> frames.addAll(trace); > >>>>> } > >>>>> - return frames.toArray(new String[frames.size()]); > >>>>> + return frames.toArray(new String[0]); > >>>>> } > >>>>> > >>>>> /** > >>>>> @@ -325,7 +325,7 @@ public class ExceptionUtils { > >>>>> while (frames.hasMoreTokens()) { > >>>>> list.add(frames.nextToken()); > >>>>> } > >>>>> - return list.toArray(new String[list.size()]); > >>>>> + return list.toArray(new String[0]); > >>>>> } > >>>>> > >>>>> /** > >>>>> @@ -438,7 +438,7 @@ public class ExceptionUtils { > >>>>> */ > >>>>> public static Throwable[] getThrowables(final Throwable > >> throwable) { > >>>>> final List<Throwable> list = getThrowableList(throwable); > >>>>> - return list.toArray(new Throwable[list.size()]); > >>>>> + return list.toArray(new Throwable[0]); > >>>>> } > >>>>> > >>>>> /** > >>>>> diff --git > >>>>> a/src/main/java/org/apache/commons/lang3/reflect/FieldUtils.java > >>>>> b/src/main/java/org/apache/commons/lang3/reflect/FieldUtils.java > >>>>> index d72dc53..553be4e 100644 > >>>>> --- a/src/main/java/org/apache/commons/lang3/reflect/FieldUtils.java > >>>>> +++ b/src/main/java/org/apache/commons/lang3/reflect/FieldUtils.java > >>>>> @@ -199,7 +199,7 @@ public class FieldUtils { > >>>>> */ > >>>>> public static Field[] getAllFields(final Class<?> cls) { > >>>>> final List<Field> allFieldsList = getAllFieldsList(cls); > >>>>> - return allFieldsList.toArray(new > Field[allFieldsList.size()]); > >>>>> + return allFieldsList.toArray(new Field[0]); > >>>>> } > >>>>> > >>>>> /** > >>>>> @@ -237,7 +237,7 @@ public class FieldUtils { > >>>>> */ > >>>>> public static Field[] getFieldsWithAnnotation(final Class<?> > cls, > >>>>> final Class<? extends Annotation> annotationCls) { > >>>>> final List<Field> annotatedFieldsList = > >>>>> getFieldsListWithAnnotation(cls, annotationCls); > >>>>> - return annotatedFieldsList.toArray(new > >>>>> Field[annotatedFieldsList.size()]); > >>>>> + return annotatedFieldsList.toArray(new Field[0]); > >>>>> } > >>>>> > >>>>> /** > >>>>> diff --git > >>>>> a/src/main/java/org/apache/commons/lang3/reflect/MethodUtils.java > >>>>> b/src/main/java/org/apache/commons/lang3/reflect/MethodUtils.java > >>>>> index bbd5019..491470d 100644 > >>>>> --- a/src/main/java/org/apache/commons/lang3/reflect/MethodUtils.java > >>>>> +++ b/src/main/java/org/apache/commons/lang3/reflect/MethodUtils.java > >>>>> @@ -878,7 +878,7 @@ public class MethodUtils { > >>>>> final boolean > >>>>> searchSupers, final boolean ignoreAccess) { > >>>>> final List<Method> annotatedMethodsList = > >>>>> getMethodsListWithAnnotation(cls, annotationCls, searchSupers, > >>>>> ignoreAccess); > >>>>> - return annotatedMethodsList.toArray(new > >>>>> Method[annotatedMethodsList.size()]); > >>>>> + return annotatedMethodsList.toArray(new Method[0]); > >>>>> } > >>>>> > >>>>> /** > >>>>> diff --git > >>>> a/src/main/java/org/apache/commons/lang3/reflect/TypeUtils.java > >>>>> b/src/main/java/org/apache/commons/lang3/reflect/TypeUtils.java > >>>>> index 2a6ccd0..f9df8c6 100644 > >>>>> --- a/src/main/java/org/apache/commons/lang3/reflect/TypeUtils.java > >>>>> +++ b/src/main/java/org/apache/commons/lang3/reflect/TypeUtils.java > >>>>> @@ -1149,7 +1149,7 @@ public class TypeUtils { > >>>>> } > >>>>> } > >>>>> > >>>>> - return types.toArray(new Type[types.size()]); > >>>>> + return types.toArray(new Type[0]); > >>>>> } > >>>>> > >>>>> /** > >>>>> diff --git > >>>> a/src/main/java/org/apache/commons/lang3/text/StrTokenizer.java > >>>>> b/src/main/java/org/apache/commons/lang3/text/StrTokenizer.java > >>>>> index c9ab666..97fae7d 100644 > >>>>> --- a/src/main/java/org/apache/commons/lang3/text/StrTokenizer.java > >>>>> +++ b/src/main/java/org/apache/commons/lang3/text/StrTokenizer.java > >>>>> @@ -604,10 +604,10 @@ public class StrTokenizer implements > >>>>> ListIterator<String>, Cloneable { > >>>>> if (chars == null) { > >>>>> // still call tokenize as subclass may do some > work > >>>>> final List<String> split = tokenize(null, 0, 0); > >>>>> - tokens = split.toArray(new String[split.size()]); > >>>>> + tokens = split.toArray(new String[0]); > >>>>> } else { > >>>>> final List<String> split = tokenize(chars, 0, > >>>>> chars.length); > >>>>> - tokens = split.toArray(new String[split.size()]); > >>>>> + tokens = split.toArray(new String[0]); > >>>>> } > >>>>> } > >>>>> } > >>>>> diff --git > >>>>> > a/src/main/java/org/apache/commons/lang3/time/DurationFormatUtils.java > >>>>> > b/src/main/java/org/apache/commons/lang3/time/DurationFormatUtils.java > >>>>> index 83af2e0..4a75237 100644 > >>>>> --- > >>>> a/src/main/java/org/apache/commons/lang3/time/DurationFormatUtils.java > >>>>> +++ > >>>> b/src/main/java/org/apache/commons/lang3/time/DurationFormatUtils.java > >>>>> @@ -564,7 +564,7 @@ public class DurationFormatUtils { > >>>>> if (inLiteral) { // i.e. we have not found the end of the > >>>> literal > >>>>> throw new IllegalArgumentException("Unmatched quote in > >>>>> format: " + format); > >>>>> } > >>>>> - return list.toArray(new Token[list.size()]); > >>>>> + return list.toArray(new Token[0]); > >>>>> } > >>>>> > >>>>> > >>>>> > >> > //----------------------------------------------------------------------- > >>>>> diff --git > >>>>> a/src/main/java/org/apache/commons/lang3/time/FastDatePrinter.java > >>>>> b/src/main/java/org/apache/commons/lang3/time/FastDatePrinter.java > >>>>> index a5edb28..888d3fb 100644 > >>>>> --- > a/src/main/java/org/apache/commons/lang3/time/FastDatePrinter.java > >>>>> +++ > b/src/main/java/org/apache/commons/lang3/time/FastDatePrinter.java > >>>>> @@ -160,7 +160,7 @@ public class FastDatePrinter implements > >> DatePrinter, > >>>>> Serializable { > >>>>> */ > >>>>> private void init() { > >>>>> final List<Rule> rulesList = parsePattern(); > >>>>> - mRules = rulesList.toArray(new Rule[rulesList.size()]); > >>>>> + mRules = rulesList.toArray(new Rule[0]); > >>>>> > >>>>> int len = 0; > >>>>> for (int i=mRules.length; --i >= 0; ) { > >>>>> diff --git > >>>>> > >> > a/src/test/java/org/apache/commons/lang3/concurrent/EventCountCircuitBreakerTest.java > >> > b/src/test/java/org/apache/commons/lang3/concurrent/EventCountCircuitBreakerTest.java > >>>>> index b3fb5cf..2819006 100644 > >>>>> --- > >>>>> > >> > a/src/test/java/org/apache/commons/lang3/concurrent/EventCountCircuitBreakerTest.java > >>>>> +++ > >>>>> > >> > b/src/test/java/org/apache/commons/lang3/concurrent/EventCountCircuitBreakerTest.java > >>>>> @@ -407,7 +407,7 @@ public class EventCountCircuitBreakerTest { > >>>>> */ > >>>>> public void verify(final Boolean... values) { > >>>>> assertArrayEquals(values, > >>>>> - changedValues.toArray(new > >>>>> Boolean[changedValues.size()])); > >>>>> + changedValues.toArray(new Boolean[0])); > >>>>> } > >>>>> } > >>>>> } > >>>>> > >>>>> > >> > >> --------------------------------------------------------------------- > >> 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 > >
