[jira] [Closed] (COLLECTIONS-756) CollectionUtils.filter(..) broken with blank Collections.singleton

["Alex Herbert (Jira)" <ji...@apache.org>]

     [ https://issues.apache.org/jira/browse/COLLECTIONS-756?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Alex Herbert closed COLLECTIONS-756.
------------------------------------
    Resolution: Not A Problem

From the Javadoc for {{Collections.singleton(T o)}}:

{noformat}
Returns an immutable set containing only the specified object.
{noformat}

If the set is immutable you cannot expect any function to be able to change it based on a filter.

This will throw an exception:

{code:java}
Collections.singleton("").clear();
{code}

So don't expect CollectionUtils to be able to remove the blank string.




> CollectionUtils.filter(..) broken with blank Collections.singleton
> ------------------------------------------------------------------
>
>                 Key: COLLECTIONS-756
>                 URL: https://issues.apache.org/jira/browse/COLLECTIONS-756
>             Project: Commons Collections
>          Issue Type: Bug
>          Components: Collection
>    Affects Versions: 4.4
>            Reporter: noname713705
>            Priority: Major
>
> When using {{CollectionUtils.filter(..)}}, if the passed collection is initialized with jdk {{Collections.singleton(..)}} and only contains an {{isBlank(..)}} string, the method will throw an exception instead of removing blank item as expected. Tested with commons-collections:4.4 and java8.
> All can be resumed with
> {code:java}
> CollectionUtils.filter(Collections.singleton(" "), StringUtils::isNotBlank); {code}



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