Affects Version/s: 4.1
Fix Version/s: None
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.
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.