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https://issues.apache.org/jira/browse/LANG-1406?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16604572#comment-16604572
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ASF GitHub Bot commented on LANG-1406:
--------------------------------------
Github user HiuKwok commented on the issue:
https://github.com/apache/commons-lang/pull/340
To whom who interested in this issue, here is some founding that I
discovered throughout this month of issue solving.
Problem:
- The exception would happened when any String object passed in with
unicode character. In order to achieve ignore case replacement, the internal
logic would first transform both `text` and `SearchString` to lowerCase( ) for
comparaition.
- However if anyone passion enough to digger deeper into the src logic of
`.toLowerCase( )`. Certain unicode character would be denormalized. In this way
the result String length would tend to longer than original length(). Example
like:
So making use of the transformed String, Out bound exception would happen
when trying to access the index that doesn't access at all (3 in this case vs 2
in length before lowerCase).
Flow:
- So the first thought into my mind is, why dun just normalize both `text`
and `searchString` before performing ignore case comparation? In this way the
String length would always stay consistence no matter `toLowerCase( )` or
`toUpperCase( )` 3 -> 3. However the another problem would emerged, as you may
noticed, while the String mentioned above denormalize, it would turn into a
UpperCase I and a dot sign.
- But what happen if the search pattern emerge into searchText in decompose
form. In this case let say I am trying to match a upper [I]. Then mismatch
would happen and this is certain not the desire behavior of this method I
believe.
BTW I Drafted a simple main method to demonstrate how mismatch would happen
in here.
https://github.com/HiuKwok/commons-lang/blob/master/src/main/java/com/hiukwok/test.java#L10-L20
> StringIndexOutOfBoundsException in StringUtils.replaceIgnoreCase
> ----------------------------------------------------------------
>
> Key: LANG-1406
> URL: https://issues.apache.org/jira/browse/LANG-1406
> Project: Commons Lang
> Issue Type: Bug
> Components: lang.*
> Reporter: Michael Ryan
> Priority: Major
>
> STEPS TO REPRODUCE:
> {code}
> StringUtils.replaceIgnoreCase("\u0130x", "x", "")
> {code}
> EXPECTED: "\u0130" is returned.
> ACTUAL: StringIndexOutOfBoundsException
> This happens because the replace method is assuming that text.length() ==
> text.toLowerCase().length(), which is not true for certain characters.
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