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https://issues.apache.org/jira/browse/LANG-770?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13227221#comment-13227221
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Marcos VinÃcius da Silva commented on LANG-770:
-----------------------------------------------
Seems that the piece of code in the description doesn't exists anymore. The
initial buffer size is being calculated as:
{code}
int noOfItems = endIndex - startIndex;
....
StringBuilder buf = new StringBuilder(noOfItems * 16);
{code}
Using this implementation solves the issue?
> StringUtils.join(Object[]) performance issue if .toString() is not trivial
> --------------------------------------------------------------------------
>
> Key: LANG-770
> URL: https://issues.apache.org/jira/browse/LANG-770
> Project: Commons Lang
> Issue Type: Bug
> Reporter: Joe Barnett
>
> I have some code that builds syntax trees, and then uses a combination of
> TreeNode.toString() and StringUtils.join() to recursively convert that syntax
> tree to a String representation.
> example .toString() of a SumNode class, where children is a TreeNode[]:
> public String toString() {
> return StringUtils.join(children, "+");
> }
> The problem is, StringUtils.join(Object[], String, int, int) is trying to be
> too smart about preallocating the StringBuffer size it uses internally, as it
> does:
> bufSize *= ((array[startIndex] == null ? 16 :
> array[startIndex].toString().length())
> + separator.length());
> followed by implicitly calling .toString() on each object in the array:
> buf.append(array[i]);
> For deep syntax trees, this results in incredibly bad performance, as when
> traversing the syntax tree, every time we go to the first node, we re-expand
> the entire tree below that node (which does the same thing with the first
> node below that, etc).
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