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https://issues.apache.org/jira/browse/MYFACES-3130?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16601162#comment-16601162
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Rapster commented on MYFACES-3130:
----------------------------------
[~markoc50] I think using foreach loop is the way to go as long the unlerlying
call does not involve recursive call or sucession of loops (as it will
overstock the stack memory and the heap, the reason of your issue actually).
Basically, something like this IMO is not necessary:
{code:java}
for (int i = 0; i < childCount; i++)
{
UIComponent child = component.getChildren().get(i);
if (!child.isTransient())
{
_markInitialState(child);
}
}
{code}
_markInitialState is only a setter call, so no risk to overtsock the heap. On
the other hand, this sample makes perfectly sense
{code:java}
for (int i = 0; i < childCount; i++)
{
UIComponent child = getChildren().get(i);
if (child.visitTree(context, callback))
{
return true;
}
}
{code}
UIViewRoot#visitTree implies components visitTree calls, which can lead to
snowball effect so better to avoid creation of iterator as it can be quickly
huge.
I'm just sharing my thought, 'cause foreach is the recommended way to go, there
are of course few exceptionnal cases
> [perf] Avoid unnecessary AbstractList$Itr instances
> ---------------------------------------------------
>
> Key: MYFACES-3130
> URL: https://issues.apache.org/jira/browse/MYFACES-3130
> Project: MyFaces Core
> Issue Type: Improvement
> Components: JSR-314
> Environment: myfaces core trunk
> Reporter: Martin Kočí
> Assignee: Thomas Andraschko
> Priority: Major
> Fix For: 2.3.0
>
> Attachments: MYFACES-3130-example.patch, MYFACES-3130-part2.patch,
> UIViewRoot-MYFACES-3130.patch
>
>
> Similar issue: MYFACES-3129
> loop from java 5:
> for (Object object: objects)
> creates new instance of AbstractList$Itr, if objects are instance of
> ArrayList.
> Similar situation is with explicit .iterator() call.
> In my testcases, it is about ~ 100 000 instances per request/response.
> Creation itself is cheap, but triggers GC lately.
> I suggest to use old index-style for (i = 0; i < childCount; i++) if
> possible. Are there any rawbacks of index-based iteration?
> Children is List and as implementation detail we know that it is instance of
> ArrayList.
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