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https://issues.apache.org/jira/browse/COLLECTIONS-604?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16066266#comment-16066266
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Jonas Holtkamp commented on COLLECTIONS-604:
--------------------------------------------
[~kinow] No feedback from his side, so I'd start implementing some example
cases on the weekend.
> More uniform safe-null methods in CollectionUtils
> -------------------------------------------------
>
> Key: COLLECTIONS-604
> URL: https://issues.apache.org/jira/browse/COLLECTIONS-604
> Project: Commons Collections
> Issue Type: Bug
> Components: Collection
> Affects Versions: 4.1
> Reporter: Bruno P. Kinoshita
> Assignee: Bruno P. Kinoshita
> Priority: Minor
> Attachments: COLLECTIONS-604.csv
>
>
> Currently, there are 65 public methods in `CollectionUtils`. And 53 without
> the deprecated ones. Out of these, 24 handle `null` arguments. The remaining
> methods throw a `NullPointerException` (NPE) at some part of its code.
> The methods that handle nulls, throw NPE, or return empty columns, boolean
> values, or just doesn't do anything.
> As a user of the API, I would expect a more uniform behaviour across the
> methods of `CollectionUtils`. COLLECTIONS-600 address one of these methods.
> `removeAll` (2x) and `retainAll` (2x) both state that a NPE will be thrown if
> either parameter is `null`. However, they never check if the values are null,
> and instead allow the code to run until a NPE is thrown.
> And the following code shows that `isEmpty` and `isFull` behave differently
> too.
> {code:java}
> Collection<String> c = null;
> System.out.println(CollectionUtils.isEmpty(c)); // return true
> System.out.println(CollectionUtils.isFull(c)); // throws a NPE
> {code}
> If I don't have to worry about `null`s with `#isEmpty`, I would expect the
> same from its related-method `#isFull`.
> What would be a good approach for it? Define a behaviour to all methods? Or
> leave as is, but add more documentation?
> There are a few methods that can easily be updated to check for `null`
> values. Others would require a bit more thinking. An example if the method in
> question for COLLECTIONS-600. It checks equality of collections, and when
> both collections are `null`, it says that they are equals. Google Guava
> [Iterables#elementsEqual|https://github.com/google/guava/blob/312aeb938bd35b5b7c8930e19ff5d1ca38e49424/guava/src/com/google/common/collect/Iterables.java#L232]
> and
> [Iterators#elementsEqual|https://github.com/google/guava/blob/312aeb938bd35b5b7c8930e19ff5d1ca38e49424/guava/src/com/google/common/collect/Iterators.java#L274]
> do not check for null values, for what it is worth.
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