[jira] [Closed] (LANG-770) StringUtils.join(Object[]) performance issue if .toString() is not trivial

["Henri Yandell (JIRA)" <ji...@apache.org>]

     [ https://issues.apache.org/jira/browse/LANG-770?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Henri Yandell closed LANG-770.
------------------------------

    Resolution: Not A Problem

Agreed. Resolving this as Not A Problem.
                
> 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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