[COLLECTIONS-813] CollectionUtils.retainAll() not throwing proper NullPointerException(NPE)

• Type: Bug
• Status: Closed
• Priority: Major
• Resolution: Fixed
• Affects Version/s: 4.4
• Fix Version/s: 4.5.0-M1
• Assignee: Unassigned
• Reporter: Elia Bertolina
• Created: 18/May/22 10:03
• Updated: 23/May/22 07:33
• Resolved: 23/May/22 07:33

Description

The CollectionUtils.retainAll(Iterable<E> collection, Iterable<? extends E> retain, Equator<? super E> equator) does not throw a NullPointerException(NPE) when one of the parameters is null.In the documentation it is stated that an NPE will be thrown if any of the parameters is null.

However, in this test case:

public class CollectionUtils_failure_Test {
    public void test() throws Throwable {
        HashSet<Integer> hashSet = new HashSet<Integer>(1095, 1095);
        try {
             Collection<Integer> collection =
             CollectionUtils.retainAll((Iterable<Integer>) hashSet,
             (Iterable<? extends Integer>) hashSet,
             (Equator<? super Integer>) null);
             org.junit.Assert.fail();        
        }
        catch (java.lang.NullPointerException e) {
        //NPE caught and test successful
        }
    }
}

The last Equator parameter is null and a NPE should be thrown, however the method executes normally, and test case fails.