[COLLECTIONS-604] More uniform safe-null methods in CollectionUtils

• Type: Bug
• Status: Open
• Priority: Minor
• Resolution: Unresolved
• Affects Version/s: 4.1
• Component/s: Collection
• Assignee: Bruno P. Kinoshita
• Reporter: Bruno P. Kinoshita
• Created: 26/May/17 12:41
• Updated: 22/Jul/23 07:36

Description

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.

Collection<String> c = null;
System.out.println(CollectionUtils.isEmpty(c)); // return true
System.out.println(CollectionUtils.isFull(c));  // throws a NPE

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 and Iterators#elementsEqual do not check for null values, for what it is worth.

Issue Links

• is depended upon by: COLLECTIONS-600 Make CollectionUtils (in particular isEqualCollection) null-safe
• links to: GitHub Pull Request #279