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  1. Commons Collections

More uniform safe-null methods in CollectionUtils



    • Type: Bug
    • Status: Open
    • Priority: Minor
    • Resolution: Unresolved
    • Affects Version/s: 4.1
    • Fix Version/s: None
    • Component/s: Collection
    • Labels:


      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.


        1. COLLECTIONS-604.csv
          4 kB
          Bruno P. Kinoshita

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              • Assignee:
                kinow Bruno P. Kinoshita
                kinow Bruno P. Kinoshita
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